Senate G.O.P. Set to Sink Test Vote on Infrastructure Bill, Pleading for More Negotiation Time

Republicans were poised on Wednesday to block action on an infrastructure measure in the Senate, raising doubts about the fate of bipartisan efforts to strike a compromise on a nearly $600 billion bill to address the nation’s aging roads, bridges and other public-works projects.

Senator Chuck Schumer, Democrat of New York and the majority leader, opted to force the vote even though the bill was unfinished and negotiators were still haggling over key details, in an effort to keep pressure on to finalize a deal that is a major piece of President Biden’s agenda. With Democrats expected to back the move, at least 10 Republicans would have to join them to reach the 60-vote threshold to move past a filibuster and take up the measure.

But Republicans and some Democrats toiling to hammer out a final agreement urged him to hold off, saying a premature vote risked scuttling their chances of success. In a last-ditch move to delay the process, 11 Senate Republicans were readying a letter to Mr. Schumer pledging to vote to allow the debate to go forward on Monday if a deal had been finalized by then.

“This vote is not a deadline to have every final detail worked out — it is not an attempt to jam anyone,” Mr. Schumer said on the Senate floor ahead of the vote. “The bipartisan group of senators will have many opportunities to make their agreement the base of the bill, even if they need a few more days to finalize the language.”

Still, in the absence of final legislation, Republicans warned on Tuesday that they would block the infrastructure debate.

“I think there are a number of Republicans that want to be for an infrastructure bill, who are waiting for this process to conclude in hopes that it will be something that they can vote for,” said Senator John Thune of South Dakota, the No. 2 Republican. The negotiators, he said, “feel like they’re in a good place, but they’re not done yet, which is why I think it’s a mistake for Schumer to try and rush this.”

In the month since Mr. Biden and a group of 10 Republican and Democratic senators announced a deal on an infrastructure framework, negotiations have focused on how to structure and finance the legislation. After a marathon of virtual meetings Sunday and Monday, the group met late into the night on Tuesday to hammer out the details.

“I think people basically have an objection to voting for something that they don’t know what they’re voting for,” Senator Bill Cassidy, Republican of Louisiana, said as he entered an evening meeting in the Capitol. “There’s something about having something to look at — a piece of paper with stuff written on it — that gives people comfort to support.”

It is unclear what will happen to the legislation if, as expected, Republicans follow through with their threats block it. Mr. Schumer could try to bring it up again at a later date, but he has not said whether he would do so.

The legislation is an integral part of Mr. Biden’s $4 trillion economic agenda, as Democrats hope to pair it with a $3.5 trillion package to fund new investments in health care, paid leave for workers, climate change provisions and other priorities. Unlike the infrastructure bill, Democrats expect to get that second measure to the president’s desk without the support of any Republicans.