As the U.S. halts military aid to Kyiv, how long can Ukraine continue to fight Russia?

U.S. military aid for Ukraine has been halted following the spectacular falling-out between President Donald Trump and Ukraine’s leader Volodymyr Zelenskyy, leaving the country in an extremely precarious situation, defense strategists say.

An anonymous White House official and U.S. official told CNBC’s partner network NBC News on Monday that military support had been halted while an assessment of the situation is carried out.

“The president has been clear that he is focused on peace. We need our partners to be committed to that goal as well. We are pausing and reviewing our aid to ensure that it is contributing to a solution,” the officials confirmed to NBC News and other media outlets.

The White House has not yet publicly commented on the statement but Ukraine’s Prime Minister Denys Shmyhal on Tuesday gave Kyiv’s reaction. He began by thanking the U.S. for its support and said Kyiv was “working and doing everything to provide our armed forces with everything they need.”

“Regardless of the discussions about the possibility of stopping [military aid] — we will absolutely calmly continue to work with the U.S., Congress, with the Trump administration and with him personally through all available diplomatic channels so that Ukraine and the U.S. continue our struggle for a just, lasting, stable peace in Ukraine, on the European continent.”

If the aid pause is confirmed, the move would be unprecedented but not surprising given the extraordinary spat between the leaders at the Oval Office on Friday, which ended with President Zelenskyy leaving the White House with haste and a multi-billion dollar critical minerals deal unsigned.

Defense strategists say that if the U.S. immediately withdraws all military support for Ukraine, which needs a continuous flow of weaponry and munitions to fight against Russia after already three years of war, the outlook is undoubtedly negative.

“This decision is not about economics. It is driven fundamentally by Trump’s view that Russia is willing to do a peace deal, and only Ukraine is the obstacle,” Malcolm Chalmers, deputy director-general at defense think tank RUSI, said Tuesday in reaction to the reported halting in U.S. military aid.

“But there is no evidence that Russia would be prepared to accept a deal, and what that would be. Indeed this decision will encourage Putin to ask for more — including Ukrainian demilitarisation and neutrality,” he said in emailed comments.

Chalmers noted that the “nightmare scenario” now is that the U.S. and Russia announce a deal soon, and then tell Ukraine and Europe to “take it or leave it.”

“What will count most of all is how far the U.K. and Europe are prepared to help Ukraine in defiance of the U.S. Recent estimates suggest that only 20% of total military hardware supplied to Ukrainian forces is now from the U.S., 55% is home-produced in Ukraine and 25% from Europe and the rest of the world, but the 20% is the most lethal and important. Ukraine will not collapse — they already experienced an aid cutoff last year, but the effect will be cumulative,” he said.

The Kremlin has already reacted to the news on Tuesday, saying it hoped Ukraine would be encouraged to seek a peace deal as a result.

“Of course, we still need to learn the details. But if this is true, then this decision could indeed push the Kyiv regime toward the peace process,* Press Secretary Dmitry Peskov told reporters Tuesday, according to an NBC News translation.

Posing the question as to whether the Trump administration can stop the immediate shipment of military aid, defense strategists at the Center for Strategic and International Studies (CSIS) said earlier this week that, “yes, at least in part.”

“The bad news is that U.S. funding for military aid to Ukraine is now depleted. The good news is that a steady stream of American equipment will continue to flow to Ukraine from previously announced commitments — if Trump allows it,” Mark F. Cancian and Chris H. Park, said in analysis published Saturday that posed the question, “Is Ukraine now doomed?.”

“Drawdown equipment is still being shipped. The Trump administration could direct that shipments cease despite announcements by the previous administration,” they noted.

“More difficult would be stopping shipments of newly produced weapons from contracts Ukraine signed with the defense industry, though with funds provided by the United States. Legally, those belong to Ukraine” they noted, with the caveat that Trump’s team “may be able to divert deliveries to U.S. forces” by using protocols that cite “national requirements.”

Although that claim would be a stretch, the Trump administration has not hesitated to use emergency authorities “for its political goals,” they noted.

What happens on the battlefield going forward depends heavily on the amount of equipment delivered, they concluded.

“The bottom line: Prospects for Ukraine are bleak. In the best case, U.S. and European aid continues, which is enough for Ukraine to stabilize the front lines, blunt Russian attacks, and buy time for a negotiated settlement, perhaps with Russia more willing to make a deal as its casualties pass the 1 million mark.”

“In the worst case, the United States cuts off shipments of equipment. What Ukraine receives from the Europeans, other global sources, and its own industry will keep its forces in the field but with declining capabilities. Russian attacks will gain more and more territory; at some point, Ukrainian lines will break. Ukraine will have to accept an unfavorable, even draconian peace.”

The status of military aid for Ukraine is opaque, with some funds “committed” or “obligated” but not yet “disbursed.” There can be long delays between the obligation and disbursement stages because equipment takes time to produce, and manufacturers get progress payments over time as equipment is delivered, the CSIS strategists noted.

There has been a festering argument between Trump and European allies as to the amount of military aid that has been given to Ukraine, be it military, humanitarian or financial aid, although the picture is murky as to what funds and support has been allocated.

The Kiel Institute for the World Economy, widely seen as an accurate and impartial source tracking funding for Ukraine, summarized the aid picture in its latest assessment in February like this:

“Europe as a whole has clearly overtaken the U.S. in terms of Ukraine aid. In total, Europe has allocated 70 billion euros [$73.6 billion] in financial and humanitarian aid as well as 62 billion euros in military aid. This compares to 64 billion euros in military aid from the US as well as 50 billion euros in financial and humanitarian allocations.”

Tensions between Washington and Kyiv had been rising steadily since Trump’s inauguration in January, and further when the U.S. began preliminary talks with Russia, excluding Ukraine, for a path to peace.

Trump had already threatened to withdraw U.S. support for the war-torn country if Zelenskyy didn’t sign a coveted critical minerals deal with the U.S., telling him Friday: “You either make a deal, or we are out.”

European leaders have already hastily scrambled to discuss what role they could have in Ukraine — and what ongoing support they can give Kyiv — in a postwar scenario that could be thrust onto the country.

The bloc appears to be readying itself to fill any defense spending gap by the U.S. with European Commission President Ursula von der Leyen on Tuesday announcing plans to increase defense spending that could potentially mobilize as much as 800 billion euros.

“Europe is ready to massively boost its defense spending. Both, to respond to the short-term urgency to act and to support Ukraine but also to address the long-term need to take on much more responsibility for our own European security,” she said in a press statement.

But given Kyiv and Europe’s apparent exclusion from early talks on how to end the war, and with no security guarantees spelled out by the U.S. for Ukraine, the outlook is looking uncertain as to what Europe’s role will be.

If the U.S. halts all military aid shipments to Ukraine, the move firmly puts the ball in Europe’s court as to how, to what extent and indeed whether they are willing to step into the breach to help Ukraine.

CSIS’ strategists stress that the U.S. is not the only equipment supplier to Ukraine.

“As calculated by Germany’s Kiel Institute, European military aid for Ukraine has been comparable to that of the United States, at roughly $1.8 billion per month. European aid was especially critical in late 2023 and early 2024 when the United States ran out of funds while Congress debated the next aid package,” they noted.

“The European Union also approved using frozen Russian sovereign assets to support Ukraine’s military needs. The bad news is that the Europeans are already supplying as much as they can, given the deteriorated state of their defense industry. Further, if the United States ceases aid, many European countries will also likely scale back,” they said.