U.S. military aid to Ukraine has also been suspended in the past, when under the previous administration, the continuation of aid was hotly debated in Congress. As a result, Ukraine says it is better prepared this time round.

"Ukraine already produces more than 30 percent of the weapons, equipment and ammunition it needs to defend itself. We are working steadily toward meeting the 50 percent target. I am confident that we will reach this goal this year," said Ukrainian Prime Minister Denis Shmyhal.

For Ukraine, it is crucial to know exactly which deliveries have now been stopped, as a large number were in the final stages of completion. Some had also been approved by Congress, for which, according to the Ukrainian presidential office, strict legal procedures need to be followed.

"It seems that this decision concerns weapons and armored vehicles as well as ammunition that is not yet on Ukrainian soil. So everything that was on its way to Ukraine via Poland, has been completely stopped, at least for a while," said Igor Gretskiy, who is a research fellow at the Tallinn-based International Center for Defense and Security.

"What is also very important is the part that cannot be touched. In other words, whether the intelligence information that the U.S. has shared with the Ukrainians has been put on hold or whether it is still being shared, and if so, to what extent," said Estonian Defense Forces (EDF) reserve Maj. Gen. Neeme Väli.

The Ukrainians have already indicated that they are analyzing which items could be sourced from international markets or substituted with European production.

According to Maj. Gen. Väli, the biggest problem for Ukraine is with the systems produced in the U.S. for which Europe has no equivalent. One example is the Patriot long-range air defense system. How long Ukraine will be able to survive without U.S. help is difficult to say, said Maj. Gen. Väli.

"We don't know what they have or how much. And it certainly depends on how much more intense the fighting becomes than it is at present, because in the last couple of weeks the intensity has been a little bit lower. The question now is whether Russia has the strength to try to take advantage of this pause," Maj. Gen. Väli said.

"The Ukrainian Defense Forces have quite a large amount of ammunition in storage, which they will be able to cope with until at least the end of spring or the beginning of summer. It depends on the intensity of the fighting," Gretskiy said.

The Estonian Defense Forces (EDF) have so far declined to comment on the issue.

---

Follow ERR News on Facebook and Twitter and never miss an update!