US Treasury Secretary Janet Yellen has said that the United States and the G7 countries are "absolutely committed" to supporting Ukraine and called on Congress to approve urgent military and budget support.

According to Reuters, Yellen said that she fears that Russia may be emboldened by domestic debates in the United States and other countries about continuing to help Ukraine.

"I do fear that Russia is beginning to see signs that the U.S. and our allies are tiring, or finding it more difficult to find ways to support Ukraine, and that gives them hope that they can outlast us and wait for our resolve to crumble," she said.

Yellen said she had many conversations about using frozen Russian assets, and this issue will be discussed at a meeting of the G7 countries on Wednesday.

She also noted that a number of possibilities are being discussed, ranging from full confiscation of assets to using them as collateral. Washington is "very supportive" of recent EU initiatives to confiscate interest on excess profits earned from seized Russian assets, the official said.

Yellen added that neither option was ruled out, but pointed out that Ukraine would also not be able to use the entire amount at once, even if all frozen assets were confiscated.

Reuters sources said that one of the most promising proposals under consideration is to use the interest from frozen Russian assets as collateral for loans or bonds issued to help Ukraine, which would not require the seizure of assets.

Yellen said that Western officials were assessing the risks associated with any repercussions, including Russian threats, but expressed confidence that they could be mitigated.

Earlier, Polish Prime Minister Donald Tusk said that the West should use all frozen Russian assets, not just their excess profits, to help Ukraine.

The EU heads of state and government summit on 21 March agreed that the EU would continue to work on a plan to use the profits from the frozen assets of the Russian central bank, specifically to arm Ukraine.

On 20 March, EU chief diplomat Josep Borrell proposed redirecting the interest earned on frozen Russian assets to Ukraine. According to the plan, 90% of the funds would go to a fund to cover the cost of weapons for Ukraine.