Joe Biden has threatened to veto a Republican bill to provide aid to Israel but not Ukraine.
"In contrast to the President's national security package, this bill provides no aid whatsoever to Ukraine. This is an urgent requirement," the White House's Office of Management and Budget said.
US support is vital to Ukraine, with America committing almost $70bn in assistance as of 31 July - far more aid than any other nation - according to the Kiel Institute for the World Economy.
But divisions have recently emerged in the House and among potential presidential candidates, with Republicans criticising the level of support.
Explained: Joe Biden wants Congress to provide $106bn in supplemental funding, with the bulk of the money going to bolster Ukraine's defences and the remainder split among Israel, the Indo-Pacific and border enforcement.
But the House elected Republican Mike Johnson as speaker last week, who raised concerns about funding for Ukraine and suggested he would not back Mr Biden's bill.
