Several Republican senators walked out of a classified briefing on Ukraine, after President Volodymyr Zelensky unexpectedly cancelled his appearance to appeal for continued US funding.

Mr Zelensky had been due to update the senators on the latest developments in the conflict with Russia and press for them to support a procedural vote expected Wednesday on an emergency aid package that includes more than $60 billion for Kyiv.

The cash has been held up for weeks by a dispute in Congress, as the White House has warned that existing funds will run out by the end of the year and that Russia’s President Vladimir Putin could win the war if lawmakers fail to act.

The briefing descended into a row over the border crisis. Utah’s Mitt Romney left early, confirming that “a number” of his Republican colleagues had followed suit, angry that they heard nothing on their demand that Ukraine aid be coupled with action on the migrant crisis at the US-Mexico border.

It comes as Treasury Secretary Janet Yellen said that the United States would be “responsible for Ukraine’s defeat” if Congress fails to approve the Biden administration’s latest multi-billion-dollar funding request for the war-torn country.

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