Senate Democrats are convening for an emergency caucus meeting Tuesday night after Sen. Joe Manchin said he is opposed to their massive reconciliation spending bill, throwing into extreme doubt whether President Biden's signature legislative priority – and the bevy of progressive policies in it – can pass.

"This session has… led to moments of deep discontent and frustration. That frustration was evident in the past week as nearly all of us were disappointed by the decision to delay floor consideration of the Build Back Better Act because Senator Manchin could not come to an agreement with the president," Senate Majority Leader Chuck Schumer, D-N.Y., wrote to Senate Democrats Monday.

Schumer said in the sharp letter that the Senate will vote on the reconciliation bill nevertheless, and "will keep voting on it until we get something done." The majority leader also said the Senate will vote on changing the legislative filibuster, which Manchin also opposes. 

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Sen. Joe Mancin, D-W.Va., delivers remarks to reporters at the U.S. Capitol in Washington, Nov. 1, 2021. (REUTERS/Jonathan Ernst)

DO WEST VIRGINIANS BACK JOE MANCHIN'S OPPOSITION TO BUILD BACK BETTER? 

"To further discuss these critical issues, we will hold a virtual Special Caucus on the evening of Tuesday, December 21, the longest night of the year," Schumer wrote in the letter.

Manchin's office did not immediately respond to a request for comment from Fox News about whether he will be in attendance on the virtual caucus meeting. He was one of the first Democrats to leave an in-person caucus lunch last week. Punchbowl News reported Tuesday morning the senator was unsure if he would attend.

Manchin's decision to oppose the reconciliation bill roiled Democrats from the Senate to the White House and beyond, inspiring biting statements from all corners of the party, including White House press secretary Jen Psaki.

Senate Majority Leader Chuck Schumer, D-N.Y., speaks to the media after a Democratic policy luncheon, Tuesday, Oct. 19, 2021, on Capitol Hill in Washington. (AP Photo/Jacquelyn Martin)

Fox News confirmed, as first reported by Politico, that Biden and Manchin spoke Sunday night and may be open to further negotiations on the president's agenda next year. But Manchin tore into the White House and Senate Democrats in a Monday radio interview on MetroNews Talkline with Hoppy Kercheval in West Virginia. 

MANCHIN SAYS HE ‘CANNOT VOTE’ FOR BUILD BACK BETTER: ‘I’VE DONE EVERYTHING HUMANLY POSSIBLE'

"I gave Schumer exactly the philosophical beliefs and the amount of money that I thought we could raise and pay for everything. And so they've had that from day one," Manchin said on the radio show. 

"The same bill I have in front of me right now that they kept putting in front of me, was the same $6 trillion bill from the beginning. The only thing that changed was the time element which would pay for things," Manchin said. "And I said, that's disingenuine (sic) to tell someone who's getting a child tax credit, it goes away for one year… when we are basically trying to collect taxes for 10 years to pay for them."

President Biden delivers remarks during an event on the South Lawn of the White House August 5, 2021 in Washington, D.C. Sen. Joe Manchin, D-W.Va., was sharply critical of how the White House handled its negotiations with him over Democrats' massive reconciliation spending bill. (Win McNamee/Getty Images)

Manchin also told Kercheval that he understands most Democrats are far to the left of him and it is tough to come to a compromise. But he said he resented tactics to "badger and beat" him into voting for the bill, particularly from the White House. 

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The conversations between Senate Democrats during the Tuesday meeting – either with or without Manchin's participation – will set the tone for whether there's any hope for Democrats' reconciliation bill, even in a heavily modified form, during the New Year. But the conversation is sure to be tense. 

"In the spirit of the season, I hope the Senator from West Virginia will at least give kids in the lowest income families a helping hand and millions of Americans suffering from diabetes affordable insulin," Senate Majority Whip Dick Durbin, D-Ill., tweeted about Manchin soon after he announced his opposition to the reconciliation bill.

"I would like to hope that there's still Democrats that feel like I do. I said I'm fiscally responsible and socially compassionate. Now, if there's no Democrats like that, then they'll have to push me wherever they want me," Manchin said Monday when asked if there's still room for him in the party. 

Fox News' Jacqui Heinrich, Jason Donner and Aishah Hasnie contributed to this report.