As the Senate barrels toward a key test vote on a bipartisan infrastructure deal, a group of Senate Republicans are pleading with Majority Leader Schumer to delay the vote until next week.

       Key Republicans in the group of senators trying to work out the deal sent a letter to Senate Majority Leader Chuck Schumer saying no GOP member will vote "yes" to start debate on any measure Wednesday, according to a senior lawmaker close to the continuing talks over how to pay for the $1.2 trillion package.

       Schumer had set the high-stakes vote to try to force progress on a top priority for President Joe Biden, but he needs the Republicans to get past the 60-vote threshold to advance legislation.

       "I don’t think any Republican votes yes tomorrow. I don’t think we should, because we’re not ready,” the senior lawmaker said looking ahead to Wednesday's vote.

       MORE: Bipartisan infrastructure negotiators scramble for deal as key funding option dropped

       Drew Angerer/Getty Images

       Senate Majority Leader Chuck Schumer and President Joe Biden speak briefly to reporters as they arrive at the U.S. Capitol for a Senate Democratic luncheon July 14, 2021 in Washington.

       Instead, the GOP negotiators’ letter to Schumer will say that Republicans, who have been warning they won't vote on advancing a bill that's not yet written, are prepared to support starting debate on Monday, the senior lawmaker said.

       The group, which has been working around the clock, along with White House officials, is "close," to a deal on how to pay for roads, bridges and other "traditional infrastructure," according to numerous members involved. They were meeting again Tuesday afternoon -- joined by senior Biden aides – to try to finalize a bill.

       The White House said it continued to support Schumer's tactics.

       MORE: Biden pushes back on inflation fears ahead of infrastructure plan vote

       But the bipartisan group of lawmakers won’t get a final agreement by Wednesday, according to multiple negotiators .Negotiators said Tuesday that there are about six remaining issues with the bipartisan bill, the thorniest of which is how to structure spending on public transit systems.

       At the same time, the senior lawmaker expects the legislation to be finalized by Monday, and that includes the nonpartisan analyses by various agencies breaking down all of the financing options, how much revenue would be produced, and a final price tag.

       Republicans, in particular, will be looking to show that the $579 billion in new spending is fully paid for.

       As of Tuesday afternoon, it didn't appear as if Schumer would delay the vote, but he could minimize the impact, should it be headed for failure.

       If it is, Schumer could switch his vote to the losing side at the last minute, enabling him as majority leader, under Senate rules, to call up the vote again for reconsideration.

       Minority Leader Mitch McConnell on Tuesday pointed to Schumer's option to bring up the bill again in a few days, after the bipartisan group has had time to complete its work.

       "No time is lost by adhering to a very simple principle, we are not going to the bill until we know what the bill is

       He could do so on Monday, when GOP members of the negotiating group say they’ll be ready to go.

       Might a failed vote Wednesday poison the well for GOP negotiators?

       No, says the senior lawmaker close to the talks, and Sen. Jerry Moran, R-Kansas, a member of the negotiating group.

       The Wednesday vote is to start debate on a shell bill because there is no final bill from the negotiators. It would serve as a placeholder should negotiators strike a final deal.

       The measure is separate from a much larger bill Biden and Democrats are pushing that would spend $3.5 trillion on so-called "human infrastructure" such as child care.

       Democrats plan to push that through the Senate with no Republican votes, using a budget tool called "reconciliation."