The $20 billion would give the country “critical support” as it defends itself “against an unprovoked war of aggression,” Yellen said on Tuesday.
It follows months of discussions between the US and its allies, including the EU, over how to use around $325 billion (£276 billion) worth of assets that have been frozen since the start of a full-scale Russian invasion of Ukraine in 2022.
In October, the G7 agreed to use the interest earned on the assets – about $3bn (£2.4bn) a year – to fund a $50bn loan over 30 years. Payments were expected to begin by the end of the year.
The EU has committed more than €18bn (£15bn) in funding in the same way.
The $50 billion is intended to ensure that Ukraine has “the resources necessary to maintain emergency services, hospitals and other foundations of its courageous resistance,” Yelen said.
This is happening at a critical moment for the forces of Ukrainian President Volodymyr Zelensky, who recently ceded territory.
It was Moscow reclaim the land in eastern Ukraine and in Russia’s Kursk – which Ukrainian troops launched an offensive in the summer – while Ukrainian troops drew a sad picture of the front lines of war.