The US has given $20bn (£15bn) to Ukraine, funded by profits from confiscated Russian assets.
The economic support forms a large part of a $50bn (£39bn) package agreed by G7 member states and announced in June.
US Treasury Secretary Janet Yellen said that financing aid through frozen assets means that Russia must “bear the costs of its illegal war, rather than taxpayers.”
This comes weeks before US President Joe Biden and Donald Trump are replaced, who he said he wants to do Ending the war in Ukraine quickly upon taking office.
The president-elect has described financial support for Kiev as a drain on US resources, casting doubt on whether aid will continue under the new administration.
The US Treasury said on Tuesday that it had transferred the $20 billion to a World Bank fund, where it will be available for Ukraine to withdraw from.
Funds handled by the World Bank cannot be used for military purposes.
Reuters reported that the administration had hoped to allocate half of the funds for military aid, but this would have required congressional approval.
There were months of delay, amid political disagreements in the House of Representatives, before $61 billion in military aid to Ukraine was approved in April.
Yellen said in a statement on Tuesday that the $20 billion would give the country a “critical infusion of support” as it defends itself “against an unprovoked war of aggression.”
It comes after months of discussions between the US and its allies, including the EU, over how to use nearly $325bn (£276bn) in assets frozen since the start of Russia's full-scale invasion of Ukraine in 2022.
In October, the G7 agreed to use interest generated from the assets – around $3bn (£2.4bn) a year – to finance $50bn in credit over 30 years. Payments were expected to begin by the end of the year.
The European Union has pledged to fund more than €18 billion (£15 billion) in the same way.
Yellen said the $50 billion is aimed at ensuring that Ukraine gets “the resources it needs to support emergency services, hospitals, and other foundations of its courageous resistance.”
This comes at a critical juncture for the forces of Ukrainian President Volodymyr Zelensky, who recently abandoned territory.
It was Moscow Reclaim the land In eastern Ukraine and in Russia's Kursk – which Ukrainian forces launched an attack on during the summer – while Ukrainian forces drew a drawing A bleak picture of the war fronts.
