Washington DC - President Joe Biden called key allies Tuesday to reassure them the United States will stand fast on Ukraine after Republican hardliners derailed funding for aid to help Kyiv's war effort.

Biden spoke with the leaders of Canada, Germany, Italy, Japan, Poland, Romania, Britain, and of the EU and NATO, along with the foreign minister of France, the White House said.

"President Biden convened a call this morning with allies and partners to coordinate our ongoing support for Ukraine," the White House said in a statement, adding that more details would be released later.

Biden had been under mounting pressure to calm shaken allies after an 11th-hour deal in the US Congress to avoid a government funding shutdown on Saturday contained no new aid for war-torn Ukraine.

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Democrat Biden has called for Republican House Speaker Kevin McCarthy to rush through new aid, saying that US support for Kyiv as it battles Russia’s invasion could not be interrupted "under any circumstances."

"Speaker McCarthy and the majority of House Republicans must keep their word and secure passage of the support needed to help Ukraine as it defends itself," Biden said on X, formerly Twitter, earlier Tuesday. "We are the indispensable nation in the world – let’s act like it."

Biden has also warned that time is short before existing funding runs out.

Russia has pounced on the chaos in Washington, with the Kremlin saying on Monday that Western war fatigue would grow amid the uncertainty over US assistance for Ukraine.

White House Press Secretary said on Monday that Russian President Vladimir was "wrong" if he believes Moscow will be able to outlast Ukraine and its allies. She added that the United States would soon announce new assistance for the Ukrainian armed forces, which will be drawn from a $113 billion budget already approved by Congress.

But the disruption in an ever-more divided US political scene could upend moves to pass the fresh $6 billion in aid that Biden had been seeking. McCarthy is fighting for his political life Tuesday ahead of a vote seeking to oust him from his role as House speaker, forced by the far-right of his party that has made clear it opposes continued support for Ukraine.

The United States is by far the leading supplier of weapons and aid to Ukraine, which is trying to push forward a slow-moving counteroffensive against Russian forces that invaded in February 2022. Biden's national security advisor, Jake Sullivan, recently estimated the amount of military assistance provided to Kyiv since Russia's invasion at $47 billion. The US Congress has approved a total of $113 billion in aid for Ukraine but opposition among hardline Republicans has been spreading, including to some voters.

An ABC/Washington Post poll released September 24 showed 41% of respondents saying the United States was doing too much to support Ukraine, up from 33% in February and just 14% in April 2022.