Washington's suspension of military assistance will not lead to a sudden collapse of Ukraine's defensive lines, but it could have a real impact on the war within months, undermining air defences and precision strike capabilities in particular.
U.S. deliveries of military aid via Ukraine's western border halted at 3:30 a.m. (0130 GMT), a source with knowledge of the matter told Reuters, after U.S. President Donald Trump paused assistance late on Monday following an extraordinary clash with Ukrainian President Volodymyr Zelenskiy last week.
The move suspends any further drawdown from $3.85 billion of military aid approved by Congress that Trump inherited from his predecessor, Joe Biden. It also appears to halt deliveries of military equipment already approved by Biden.
"It's pretty significant, but not nearly as impactful as it would have been earlier in the war because Ukraine is far less dependent on direct U.S. military assistance now than it was previously," said Michael Kofman, a senior fellow at Carnegie Endowment.
"But it will definitely affect Ukraine, and the effect will become more pronounced after a couple of months as inventories become depleted," he told Reuters on Monday, shortly before the aid cut was announced.
In particular, Kyiv may now struggle to source replacements for sophisticated air defence systems used to repel regular Russian missile attacks, and precision weapons like the HIMARS missile system, which is one of Ukraine's main strike systems, with a range of 70-85 km (45-55 miles).
UKRAINE HAS STEADILY REDUCED DEPENDENCE ON US WEAPONRY
Ukraine depended heavily on U.S. military aid after the Russian invasion in February 2022, but survived a months-long holdup in supplies in the first half of 2024 as Republicans initially refused to sign off on a major assistance package.
That delay was eventually felt on the front, where Ukrainian soldiers complained for months of significant shortages of artillery shells, helping put Moscow's forces back on the front foot after Ukraine's failed 2023 counteroffensive.
This time, any loss of U.S. artillery supplies should not deal as big a blow, as Europe has significantly stepped up its supplies of shells, and other countries have contributed directly or indirectly.
Ukraine also now uses domestically made drones for a majority of battlefield strikes, defence experts said.
"Artillery has not lost its place on the field of battle, but we see that the war has changed and it is now based on drones. Artillery needs to be there, it changes the enemy’s intentions, but the base is drones," said Roman Kostenko, secretary of Ukraine's parliamentary committee on national security, defence and intelligence.
He said that in 2024, 65% of Russian soldiers killed or wounded by Ukraine were hit by drones, while only 20% were hit with artillery, and only 10% with American artillery.
But the loss of 155mm artillery shells, of which the United States was the largest supplier, looks to be a problem.
"I know that at the moment we have some reserves, and I think that, with the current intensity of fighting they should last until about the middle of summer," he told Reuters.
WILL US STOP OTHERS GIVING KYIV ITS ARMS OR INTELLIGENCE?
Serhiy Rakhmanin, a lawmaker on the parliamentary committee, said much would now depend on whether the United States decides to block producers from third countries that hold U.S. production licences and are ready to continue supplying Kyiv with weapons and ammunition.
The United States is Ukraine's single largest military donor, having delivered or allocated over 64 billion euros' worth ($67 billion) since January 2022, data by the Kiel Institute for the World Economy shows.
Europe's military aid amounts to just under 62 billion euros.
"If our European partners have the freedom to act, if they have the time, the desire, the money and the ability to help us, this will not be a disaster," Rakhmanin told Reuters.
He pointed in particular to howitzers and air defence missiles.
Similar questions apply to the sharing of U.S. intelligence data, and whether Washington would allow it to be passed on by third countries, he added.
For now, there is no sign the United States has terminated intelligence sharing with Ukraine, although relations are under great strain as Washington engages directly with Russia to seek an end to the war in Ukraine.
"This is only a first step of disengagement, just as the re-engagement with Russia will come in several steps," said Eurointelligence, a think-tank, in a research note.
"This decision on its own is not going to affect the war in a material way, but it constitutes an important diplomatic signal."
