(Bloomberg) -- Ukrainian President Volodymyr Zelenskiy canceled an address to the US Senate as negotiations stall on $61 billion in new weaponry and other aid to his country. 

The White House has warned that the US could completely run out of resources to assist Ukraine by the end of the calendar year. Yet the package continues to be held up by Republican demands that Democrats and the White House make major concessions on immigration policy to curb a surge in migrant crossings at the US border with Mexico. 

Senate Majority Leader Chuck Schumer moved to break that impasse Tuesday by offering Republicans a vote this week on their border proposal, which is widely opposed by Democrats and unlikely to receive the 60 votes necessary.

“We’re giving them a golden opportunity,” Schumer said of Republicans. 

But the move also makes it more difficult for Republicans to oppose a procedural vote on Ukraine aid scheduled for Wednesday. Republicans, Schumer said, aren’t serious about helping Ukraine if they oppose that vote. 

Senate Republican leader Mitch McConnell, who has pushed for more aid to Ukraine, told reporters he’s urging his party to vote against the procedural motion in order to demonstrate that the GOP is serious about enacting border policy.

Schumer previously said Zelenskiy had been invited to speak via video to a Tuesday afternoon closed-door briefing for all senators on the situation in Ukraine. The Democratic leader said Tuesday Zelenskiy won’t be participating. 

--With assistance from Steven T. Dennis.

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