The US has provided $20 billion in aid to Ukraine, funded by profits from confiscated Russian assets.
Economic support is an important part of the $50 billion package announced by G7 member states in June.
US Treasury Secretary Janet Yellen said funding aid through frozen assets means Russia must “bear the costs of its illegal war, instead of taxpayers”.
It will be several weeks before US President Joe Biden is replaced by Donald Trump, who has said he wants to quickly ended the war in Ukraine as soon as he took office.
The president-elect described financial assistance to Kiev as a drain on US resources, raising doubts about whether aid would continue under the new administration.
The US Treasury Department said on Tuesday it had transferred $20 billion to a World Bank fund, where Ukraine will be able to withdraw the money.
Money handled by the World Bank cannot be used for military purposes.
Reuters news agency reported that the administration had hoped to spend half of this amount on military aid, but this would require approval from Congress.
There were months of delay, amid political wrangling in the House of Commons, before $61 billion in military aid to Ukraine was approved in April.
Ms. Yellen said in a statement Tuesday that the $20 billion would give the country “a vital source of support” as it defends itself “against an unprovoked war of aggression.”
It follows months of discussions between the US and its allies, including the EU, on how to use some $325 billion worth of assets that have been frozen since Russia’s full-scale invasion of Ukraine began. in 2022.
In October, the G7 agreed to use the interest generated by assets – about $3 billion a year – to finance $50 billion in credit over 30 years. Payments are expected to begin later this year.
The EU has pledged more than €18 billion (£15 billion) in similar funding.
The $50 billion is intended to ensure Ukraine has “the resources it needs to maintain its emergency services, hospitals and other foundations of its courageous resistance,” Ms. Yellen said.
It comes at a crucial time for Ukrainian President Volodymyr Zelensky’s forces, who recently ceded territory.
Moscow has retake the ground in eastern Ukraine and in Russia’s Kursk – where Ukrainian forces launched an offensive in the summer – while the Ukrainian army has drawn a A bleak picture of the war’s front lines.
