After the start of the Ukraine war in February 2022, Washington was able to quickly forge an international coalition to back Kiev, providing tens of billions of dollars in military aid, training Ukrainian troops, and imposing sanctions against Moscow.

"Without US support, and then... the broader European and global support, the Ukrainians would have collapsed," considered Mark Cancian, a senior advisor at the Center for Strategic and International Studies.

"The support is absolutely vital. And continuing that support is absolutely vital," he said.

International assistance from dozens of countries has been coordinated through the Ukraine Defense Contact Group, which first met in late April last year.

The meetings allow Ukrainian officials and military leaders to "update ministers on current battlefield dynamics and Ukrainian requirements so the international community can identify and provide Ukraine with the capabilities needed," Deputy Assistant Secretary of Defense for Russia, Ukraine, and Eurasia Laura Cooper told AFP.

According to Cooper, US Defense Secretary Lloyd Austin has been the main driver behind the group, with meetings held on a near-monthly basis "to intensify our efforts and coordinate our assistance and focus on winning today's fight and the struggles to come."

Ukraine's supporters are also training its soldiers -- an effort coordinated separately through the Security Assistance Group-Ukraine organization -- with US forces starting a program focused on larger-scale maneuvers last month, in addition to instruction on specific weapons systems.

Aid for Ukraine has covered almost all types of military equipment, from uniforms, small arms, and ammunition to artillery rocket systems, air defenses, and armored vehicles.

Kiev has pushed for some items that its international supporters have been reluctant to provide, including Patriot air defense systems and advanced heavy tanks -- which were eventually promised -- and others, such as long-range missiles and fighter aircraft, which have not been provided so far.

Total military assistance from the United States and other countries amounts to at least $45 billion since the start of the Ukraine war, Cooper highlighted.

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Much of that figure has come from the United States, with aid provided through direct withdrawals from American military stockpiles, as well as via orders placed with the security industry.

Cancian pointed out that the impact on US stocks "will be an increasing issue," noting that this is especially the case with artillery ammunition. At the same time, there are adequate supplies of other items.

He indicated that substitutions and purchases from other countries will likely be the solution, adding that "the aid will continue. But how it's provided will adapt."

While bipartisan backing for Ukraine assistance is generally strong, some lawmakers have called for curbs on aid, while others are pushing for it to be stepped up.

"No more money for Ukraine," Republican Representative Matt Gaetz tweeted earlier this month, but a bipartisan group of senators called in late January for aid to Kiev to be expanded to include advanced systems that Washington has not yet provided.

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