CNN  — 

House Speaker Nancy Pelosi and West Virginia Sen. Joe Manchin are at a crossroads over President Joe Biden’s agenda to transform the government’s role in the country.

The Democratic leader said Wednesday that the White House needs to sign off on a multitrillion-dollar bill expanding the social safety net before House liberals vote for a roughly $1 trillion infrastructure bill on Thursday. Manchin, a pivotal vote in the 50-50 Senate, told CNN “that won’t happen.”

“While I am hopeful that common ground can be found that would result in another historic investment in our nation, I cannot — and will not — support trillions in spending or an all or nothing approach that ignores the brutal fiscal reality our nation faces,” added Manchin in a statement. “There is a better way and I believe we can find it if we are willing to continue to negotiate in good faith.”

The back-and-forth between two high-profile Democrats highlights the dilemma facing negotiators trying to nail down an agreement by Thursday, when a crucial authorization allowing federal highway funds to flow to the states expires. With a split Senate and a tenuous hold on the House, liberal and moderate Democrats are leveraging their power to make sure their colleagues support their top priority.

House moderates want to pass the Senate’s bipartisan infrastructure bill, which would spend hundreds of billions of dollars upgrading roads, bridges, transit, rail, broadband, airports, ports and waterways.

Meanwhile, liberal House Democrats want to pass a massive proposal known as the Build Back Better Act, which would expand the child tax credit and Medicare’s ability to cover vision, hearing and dental care, fund community college and universal prekindergarten initiatives, combat climate change, and fund elder care and paid leave programs. The bill would be paid for, at least in part, by huge tax increases primarily on corporations and the wealthy.

But the conflicting demands of the two wings of the Democratic Party have put Senate Democratic leader Chuck Schumer and Pelosi in a tough spot, as progressives push to strike a deal with moderates on their once-in-a-generation bill. Pelosi said Wednesday that Democrats need to have “legislative language — not just principles” that Biden supports to move forward.

“It has to meet his standard,” she said.

But Manchin and Democratic Sen. Kyrsten Sinema of Arizona have criticized the $3.5 trillion price tag on the broader economic agenda bill, as well as individual components, including efforts to address climate change and increase the corporate tax rate. Manchin and Sinema have been engaged with the White House in negotiations over the bill all week. White House staffers met again with Sinema on Wednesday in her office on Capitol Hill.

Manchin said, “All we need to do is pass the bipartisan infrastructure bill, sit down and start negotiating in good faith. That’s it.”

Senate Budget Chairman Bernie Sanders, a Vermont independent who caucuses with the Democrats, appeared frustrated with Sinema and Manchin later Wednesday, saying they haven’t been clear on what they want in the economic agenda bill.

“I think that there has been a lot of frustration with both of those senators in that they have not come forward and said, you know, ‘This is what I want. This is what my concern has been.’ They have talked in vague terms, but we haven’t seen the specifics that we need,” he told CNN’s Anderson Cooper on “AC360.”

Pelosi didn’t rule out delaying the Thursday vote for the bipartisan infrastructure bill.

Biden huddled with Pelosi and Schumer for more than an hour Wednesday as the three worked to unite their party behind his domestic agenda. A senior administration official says there were no major breakthroughs during the meeting, which was more of an update as they discussed where moderates stand on the reconciliation package.

Regarding whether the House will vote on the bipartisan infrastructure bill Thursday, as Pelosi has indicated is still her plan as of Wednesday evening, Biden is following her lead.

Progressive Caucus Chairwoman Pramila Jayapal, a Washington state Democrat, told CNN’s Erin Burnett that she believes that the vote on the bipartisan bill will be delayed, but if Democratic leadership does go through with the vote Thursday, progressives will vote the legislation down.

“I have a feeling that it will be delayed but if we do have a vote, then we’ll vote it down and we’ll continue the negotiations, so that we can actually deliver the entirety of the President’s agenda,” Jayapal said.

If Congress does not pass the infrastructure bill, it will have to find another way to authorize highway programs at risk of expiring.

Democratic Sen. Tom Carper of Delaware, who chairs the Senate Environment and Public Works Committee, said he’s been in talks with the committee’s top Republican, Sen. Shelley Moore Capito of West Virginia, about keeping the surface transportation funding law in place until early December to give lawmakers more time to resolve their differences.

Carper explained what the impact would be if the law expired.

“Starting later this week you’d see a cascading disruption in the surface transportation projects around the country. It would start relatively small, modest, but get worse over time,” he said.

Capito said she felt “confident” an agreement to keep the law in place would be reached this week, although she said discussions include extending it just to the end of October and a final decision on the date hasn’t been made.

Sen. Dick Durbin of Illinois, the Democratic whip, said he hoped an extension of the bill ends up in a separate, broader funding bill – known as a continuing resolution – that is expected to pass Thursday to prevent a government shutdown.

But Carper said he was working other routes to get it approved because, “the powers that be aren’t anxious to add more provisions to the CR and want to keep it relatively clean.”

This story has been updated with additional developments Wednesday.

CNN’s Annie Grayer, Kaitlan Collins, Devan Cole and Ted Barrett contributed to this report.