“We cannot under any circumstances allow American support for Ukraine to be interrupted,” Mr Biden said in remarks from the Roosevelt Room after Congress voted late on Saturday to avert a government shutdown by passing a short-term funding package that dropped assistance for Ukraine in the fight against Russia.

“We have time, not much time, and there’s an overwhelming sense of urgency,” he said, noting that the funding bill lasted only until mid-November.

Biden urged Congress to negotiate an aid package as soon as possible.

But the omission of additional Ukrainian aid from the package has raised concerns in Kyiv, which relies heavily on western financial aid and military equipment in its fight against Russia’s ongoing invasion.

A little more than a week ago, lawmakers met in the Capitol with Mr Zelensky, who sought to assure them his military was winning the war but stressed that additional aid would be crucial for continuing the fight.

Yet recent voting in the House has pointed to increased US isolationism and a growing resistance to providing further aid as the war, now in its 20th month, grinds on.

In a sign of a partisan divide on the issue, nearly half of House Republicans voted to strip 300 million US dollars from a defence-spending bill to train Ukrainian soldiers and purchase weapons. The money was later approved separately, but opponents of Ukraine support celebrated their growing numbers.

Writing on Telegram, Ukrainian parliament member Oleksiy Goncharenko said on Sunday that Kyiv needed to adopt new measures to receive the continued support of both American officials and the general public. Without it, Goncharenko said, Ukrainians had “practically no chance” of defending themselves.

He set forward a list of proposals that included permanently posting Ukrainian delegates in Washington.

“We need to speak the language of money with the US: How will the United States benefit from Ukraine’s victory? What will the US get? What will American taxpayers get?” Goncharenko wrote.

“We need to change strategy. We need to act differently. Let’s fix this situation. We cannot lose.”

The war in Ukraine was a culture shock for European leaders, many of whom couldn’t possibly fathom that war on European soil was still a possibility. The European Union, a gargantuan institution with an oftentimes unwieldy, slow bureaucracy, has had to adapt to its newfound circumstances on the fly. In some respects, the EU has passed the challenge with flying colors. There was a time not so long ago when EU countries such as Germany were at the mercy of Russian natural gas, and powers outside the bloc, such as the United Kingdom, were perfectly content with allowing Russian oligarchs to park millions of dollars in their banks. Not anymore: EU imports of Russian gas have declined from 40% to slightly under 9%. A huge chunk of Russia’s foreign reserves — $300 billion — remains locked in Western accounts, and some European leaders want to use the money to assist Ukraine’s postwar reconstruction. On energy and economics, the EU has acted with remarkable speed.

But one can’t say the same on the military front. Compared with the U.S., Europe’s military contributions to Ukraine have lagged. U.S. military aid to Ukraine thus far has reached $44 billion, more than the European Union, Germany, the United Kingdom, Norway and Poland combined. European officials recognize the disparity and are trying to beef up their own military industrial complex to keep up with Ukraine’s needs on the battlefield. EU foreign policy chief Josep Borrell proposed a $21 billion fund over the next four years that would reimburse individual EU nations that donate military hardware to the Ukrainians. And a $2.1 billion fund designed to cajole member states to deliver much-needed ammunition to the Ukrainian army is already in effect.

All of these programs, however, will need to be accelerated in scale and scope if the Europeans truly believe Ukraine’s success is as vital to the Continent’s security as they say it is.

U.S. officials often talk about burden-shifting, the notion that Europe needs to take primary ownership of its own security neighborhood. This will be an interesting test to see if the Continent is up to the task.

• Oct. 3, 2023Updated 5:39 p.m. ET

Across desolate fields and shattered villages, Ukraine’s counteroffensive is confronting Russian minefields and Russian soldiers dug into elaborate trench networks.

But one unusually daunting obstacle to Ukrainian troops is a tactic adopted by Russian forces: ceding ground and then striking back.

Rather than holding a line of trenches at all costs in the face of Ukraine’s assault, security experts say, Russian commanders have employed a longstanding military tactic known as “elastic defense.”

To execute the tactic, Russian forces pull back to a second line of positions, encouraging Ukrainian troops to advance, and then strike back when the opposing forces are vulnerable — either while moving across open ground or as they arrive at the recently abandoned Russian positions.The goal is to prevent Ukrainian troops from actually securing a position and using it as a base for further advances. That is what Ukraine was able to do successfully in the village of Robotyne in the south, its biggest breakthrough in recent weeks.

“The defender gives ground while inflicting as heavy casualties as they can on the attackers with a view to being able to set the attackers up for a decisive counterattack,” said Ben Barry, a senior fellow for land war studies at the International Institute for Strategic Studies, a British research group.

This tactic is just one of several factors that have impeded more rapid progress, according to Ukrainian officials and military experts. They also cite Moscow’s use of dense minefields, networks of trenches and tank barriers, and the reluctance of the country’s NATO allies to supply advanced fighter jets and longer-range weapons sooner in the war.

Perhaps the most formidable problem for Ukraine is Russia’s large stockpiles of artillery, which have been deployed throughout the conflict and not least to repel the counteroffensive that began in June.

Elastic defense is not a new strategy, Mr. Barry said. The Soviet Union employed it during its defeat of Germany in 1943 at the Battle of Kursk, one of the biggest on the eastern front during World War II. Russia also appears to have been applying it for some time in Ukraine, especially to hamper this summer’s counteroffensive.“Historically it’s been used very successfully, but to succeed it requires good leadership and well-trained forces and to deliver decisive counterblows,” Mr. Barry said.

Assessing whether the tactic is being deployed on any given day is difficult without direct access to Russian commanders, experts said. But the Institute for the Study of War, an organization based in Washington, noted signs of it in recent days around the village of Robotyne, which fell to Ukrainian forces at the end of August.

Some significant field fortifications had changed hands several times, it said in a report this weekend, adding that Russian forces had “been conducting successful limited tactical counterattacks.”

Competing claims this week illustrated the issue: Russian forces said they had staged an assault on Ukrainian troops on the front line in the southern Zaporizhzhia region, where Kyiv has staged the main thrust of its counteroffensive, while Ukraine’s forces said they had “repelled the attacks.”

In a report on Monday, the institute said that geolocated footage and satellite imagery appeared to show that Ukraine had regained control of a trench system, southwest of Robotyne, that it had previously lost to Russian troops. Another indication of the back-and-forth nature of the fighting came on Tuesday, when Gen. Oleksandr Tarnavskyi, the head of Ukraine’s forces in the south, said that there had been an advance by his troops. It was not possible to verify his report.In recent months, Ukraine’s war has consisted of battles for tiny villages and individual trench systems — contests that can last for weeks, with each side sustaining significant casualties to secure control. Overall, however, the conflict is being fought over a front line that stretches for hundreds of miles from the small city of Kupiansk, in the northeastern region of Kharkiv, where Russian forces have been trying to advance, to the Zaporizhzhia region in the south.

Ukrainian forces have also pushed forward in the south of an eastern region, Donetsk, where fighting over Bakhmut, one of the war’s most savage battles, has not stopped since Moscow gained control of the city in May.

President Volodymyr Zelensky of Ukraine visited troops near Kupiansk on Tuesday to hand out medals and inspect military equipment, including Leopard tanks that have been donated by the country’s NATO allies in Europe. His Telegram account posted a video of him in a forest shaking hands with a small group of soldiers, who appeared to include older men — a sign of the toll the war has taken on Ukraine.

Military experts believe that Russia, too, has suffered significant losses in the course of Ukraine’s counteroffensive, though it has slowed Ukraine’s military to a crawl, in part through its elastic defense.

A key factor in the successful implementation of the tactic is the judicious use of military reserves, who can be thrown into the battle for a counterattack, said Oleksiy Melnyk, a former Ukrainian commander who is now a senior official at the Razumkov Center, a nonprofit institute in the capital, Kyiv.Moscow appeared to have begun to deploy elite airborne units to its defense in the Zaporizhzhia region, according to Mr. Melnyk, suggesting that its supply of regular reserves could be running thin — a development that Mr. Melnyk said would be “encouraging news” for Ukraine.

Michael Kofman, a senior fellow at the Carnegie Endowment for International Peace, said that if Moscow’s forces begin to retreat more than a few hundred yards at a time, and Ukrainian troops, particularly mechanized units, are able to build up enough momentum to advance in significant numbers, it would be a sign that Russia’s defensive strategy was beginning to falter.

“One of the biggest things that remains in question is whether or not the Ukrainian military will be able to achieve a breakthrough,” he said on the “War on the Rocks” podcast last week. One alternative, he said, is that “what we’re seeing is largely how this offensive was going to unfold from now until, let’s say, we get into the winter, or perhaps even through the winter.”

CNN — Western militaries are running out of ammunition to give to Ukraine, NATO and British officials warned Tuesday, as they urged the bloc’s nations to ramp up production to “keep Ukraine in the fight against Russian invaders.”

The news of possible ammunition shortfalls comes after money to buy weapons for Ukraine was not included in a stopgap spending bill the US Congress passed at the weekend to avoid a federal government shutdown.

Fresh uncertainty over the future of US aid arose Tuesday when US House Speaker Kevin McCarthy, who advocated for support of Ukraine, was oustedfrom his leadership position by Republican colleagues.

The developments are troubling news for Ukraine as the war with neighboring Russia is in its 20th month and raises questions over whether Moscow may feel able to outlast western commitment promises.

“The bottom of the barrel is now visible,” Adm. Rob Bauer of the Netherlands, the chair of the NATO Military Committee and NATO’s most senior military official, said of the West’s ammunition stockpile Tuesday during a discussion at the Warsaw Security Forum.“We give away weapons systems to Ukraine, which is great, and ammunition, but not from full warehouses. We started to give away from half-full or lower warehouses in Europe” and those stores are now running low, Bauer said.

James Heappey, minister of state for the armed forces of the United Kingdom, speaking at the same panel as Bauer, said even though stockpiles may be thin, aid for Kyiv must continue and Western countries need to increase their capacity to make more ammo.

“We have to keep Ukraine in the fight tonight and tomorrow and the day after and the day after,” Heappey said. That means, “continuing to give, day in day out, and rebuilding our own stockpiles,” he added.

Meanwhile, analysts are warning that the US “arsenal of democracy” needs to start working overtime or Ukraine’s war effort may be in trouble.