President Joe Biden’s $579 billion bipartisan infrastructure deal is being is threatened by possible Republican defections a day after it was announced, as GOP lawmakers try to kill off a much larger tax and spending package that Democrats have in the works.

The 11 Republicans in the group of 21 senators who’ve endorsed the infrastructure package are under pressure from within their party to bolt from the agreement after the president explicitly tied its signing to also getting a multi-trillion dollar tax and social spending package that Democrats will try to push through Congress without relying on any GOP support.

The threats are aimed at putting pressure on the Democratic moderates in the bipartisan group, chiefly Senators Joe Manchin of West Virginia and Krysten Sinema of Arizona, whose votes would be pivotal on the broader package.

Kansas Republican Senator Jerry Moran, who had endorsed the substance of the bipartisan deal, is wavering in support of it, according to an aide in the senator’s office.

Other GOP aides said Republican lawmakers viewed Biden as reneging on the bipartisan deal by saying he wouldn’t sign it until he also had the bigger package in hand. Even though Republicans knew Democrats would try to pass the tax and spending plan on their own, they felt Biden had pulled the rug out from under them by tying both votes together, the aides said.

Moran is seeking assurances from Manchin and Sinema that they will oppose the subsequent tax and spending package.

Any such move by Manchin and Sinema would upend the strategy Biden has laid out along with Senate Majority Leader Chuck Schumer and House Speaker Nancy Pelosi to move both pieces of strategy in tandem. Progressive Democrats are threatening the $579 billion infrastructure plan, which falls short of their objectives, without a guarantee of a $3 trillion or larger bill focused on tax increases and spending to address climate change, education costs and childcare.

Call Coming

The group of 10 senators -- five Democrats and five Republicans -- who drafted the compromise infrastructure plan that Biden endorsed Thursday has scheduled a call for 3 p.m. Friday, according to a congressional aide familiar with the matter.

White House press Secretary Jen Psaki on Friday said that the administration doesn’t believe the deal is in trouble and that the plan to move both pieces on parallel tracks was well known.

“That hasn’t been a secret. He hasn’t said it quietly,” she said.

Still, Biden was shoring up support and the White House announced he had called Sinema to thank her and reiterate his support for moving quickly on both pieces of legislation.

Read More: Biden Infrastructure Win Ramps Up Fight Over Economic Agenda

Neither Schumer nor Pelosi have votes to spare. Schumer has said the two tracks are linked; they can’t get the votes for one without the other also moving forward.

Biden’s comments Thursday that he wouldn’t sign infrastructure legislation without also having the tax and social spending bill in hand triggered a quick, and angry, response from Senate GOP leader Mitch McConnell. He accused the president of caving to the Democratic party’s left wing.

“It was a tale of two press conferences -- endorse the agreement in one breath and threaten to veto it in the next,” McConnell said. “That’s not the way to show you’re serious about getting a bipartisan outcome.”

Republican frustration among the deal’s supporters began to boil over late Thursday, just hours after the deal was announced. Lindsey Graham of South Carolina announced his support of the substance of the deal but said that Biden’s threat to block the compromise unless he gets the second package was a “dealbreaker.”

GOP Senator Susan Collins of Maine on Thursday said she opposed tying the two bills together, but didn’t indicate she was going to pull her support for the package at the time.

“I fully expect that he is going to push a second package and he made that clear as well, but there is no reason why we can’t proceed with this one,” she said.

A 21-member bipartisan Senate group put out a statement in support of the deal hours after the Biden comments tying the two packages together. And some members of the group on Thursday, when asked about them, shrugged them off publicly.

“I cannot control what Democrats do. My gosh, if I could, they wouldn’t be Democrats,” Louisiana Republican Bill Cassidy said on Fox Business. However, he later told reporters he felt “blindsided” by Biden’s remarks and was seeking clarification from the White House.

Progressives dismissed the Republican threats.

“They are looking for a way to get out of any bipartisan bill. Mitch McConnell is going to grab on to anything he can,” Representative Pramila Jayapal, head of the Congressional Progressive Caucus, said.

Biden and Democrats have made no secret in recent weeks that they planned to try to move the parts of their agenda that Republicans do not support, including rolling back some of the 2017 GOP tax cuts for the wealthy and corporations, on their own -- using the budget reconciliation process, which can bypass the Senate filibuster. Biden and Pelosi were more explicit Thursday, however, in conditioning their support for the infrastructure deal on enactment of the second package.

Those statements came as progressives in the Democratic caucuses worried that Manchin and Sinema cannot be trusted to vote for the budget-reconciliation bill once the infrastructure package they negotiated is signed into law.

While Manchin said a second bill is “inevitable,” he said he would not commit to supporting it until he see the contents. He also dismissed a $6 trillion draft proposal by Senate Budget Chairman Bernie Sanders as adding too much debt.

Psaki, when asked in a Friday press briefing whether the deal is now in trouble, said “absolutely not in our view.” She underscored that Biden’s insistence Thursday on a Democrat-only tax and social spending package alongside the bipartisan infrastructure deal was not a new position.

“The American people are quite focused on how we’re getting work done on their behalf, less focused on the mechanics of the process,” she said, adding that the sequencing and timing is up to Schumer and Pelosi. She called the GOP objections “pretty absurd.”

— With assistance by Laura Litvan, and Billy House