The government is days away from shutting down, and the Senate may not have the votes to pass the initial version of its funding bill as top Democrats press ahead on a deal with Sen. Joe Manchin that may fail Tuesday.

Manchin, D-W.Va., agreed to help Senate Majority Leader Chuck Schumer, D-N.Y., pass Democrats' social tax and spending bill last month. In exchange, Schumer promised Manchin a vote on an energy permitting reform to speed new projects. They are combining that with a government funding bill that must pass by Friday night or else trigger a government shutdown. 

However, with a major test vote with a 60-vote threshold set for Tuesday night, the legislation may not have the support to pass, with opposition coming from both parties. Manchin's office says he is still optimistic. 

"He was working the phones all weekend and has shored up several more R votes. He’s still confident there is a path to 60, this moment won’t come again, and he continues to remind his colleagues of that," a Manchin aide told Fox News Digital Monday.

MANCHIN ENERGY PROPOSAL PICKS UP KEY GOP VOTE BUT STILL FACES TOUGH PATH TO PASSAGE

Joe Manchin

Sen. Joe Manchin's office says he remains optimistic his permitting reform bill can pass. (Anna Moneymaker/Getty Images)

Schumer has also insisted he will follow through on his deal with Manchin. He said Thursday he is "working hard to have it pass."

If the vote fails, Congress will be forced to scramble to pass a government funding bill before midnight Friday. That could be a tall task with three legislative days to spare.

It is possible that Manchin's permitting reform provision will be stripped from the funding bill if it fails Tuesday night, so lawmakers can advance the rest of the package later in the week. However, that timing could be close.

Among options to help avert a shutdown, lawmakers could pass a one-day or two-day funding bill before passing a bigger package to keep the government funded until after the elections. Another possibility would be both parties in the Senate could cooperate to speed along the funding bill and beat the Friday night buzzer. 

Capito at press conference

Sen. Shelley Moore Capito says she will support a permitting reform bill from Sen. Joe Manchin. (Pete Marovich/Bloomberg via Getty Images)

SEN. JOE MANCHIN PRESSED ON HIS ENERGY PROPOSAL: 'WE NEED TO COME TOGETHER AS AMERICANS'

Other issues may also impact votes on the funding bill. According to a source, the package will include disaster relief for Jackson, Mississippi, winter heating assistance, Food and Drug Administration user fee reauthorization and more than $12 billion in new assistance for Ukraine.

Senators on both sides of the aisle say they oppose the Manchin bill for differing reasons. Many Republicans say they do not want to reward Manchin for his support of the social spending and tax bill. Others say it is weaker in certain areas than a bill proposed by Sen. Shelley Moore Capito, D-W.Va., which most Senate Republicans co-sponsored. 

Sen. Bernie Sanders, I-Vt., is pushing fellow liberal Democrats to oppose the bill because he does not want to speed along new fossil fuel projects. Sen. Elizabeth Warren, D-Mass., says she wants permitting reform and the funding bill voted on separately. Additionally, the more moderate Sen. Tim Kaine, D-Va., said he is upset about language that would give special treatment to the Mountain Valley Pipeline project in West Virginia. 

None of those Democrats have explicitly said yet that they will vote against the government funding package over the permitting reform bill. 

Sanders speaks to a reporter

Sen. Bernie Sanders says he opposes speeding permitting processes for energy projects. (Kevin Dietsch/Getty Images)

GOVERNMENT FACES POTENTIAL SHUTDOWN IF ENERGY AGREEMENT NOT REACHED

The only Republican so far on the record as planning to vote for the funding bill with Manchin's proposal is Capito herself. Capito said Thursday that a major reason for her support is its provisions boosting the Mountain Valley Pipeline.

However, her support may not lead a significant number of other Republicans to vote for Manchin's plan. Fellow Republicans attribute Capito's stance to her state, where the pipeline is considered an important project.

"She has her own issue with West Virginia there with the pipeline, and we understand that," Sen. Steve Daines, R-Mont., told Fox News Digital last week. He says he opposes the bill.

Several other moderate Republicans remain publicly undecided on where they will stand. Those Republicans include Sens. Dan Sullivan, R-Alaska, Susan Collins, R-Maine, Lisa Murkowski, R-Alaska, and Pat Toomey, R-Pa.

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Toomey, whose state borders West Virginia, said last week that he would consider the "merits of the bill" in deciding how he will vote. He said the Mountain Valley Pipeline is "very important to me."

Even if more Republicans break ranks and vote for the funding bill with Manchin's permitting reform, it is still unclear if it will be enough for the bill to clear the 60-vote filibuster threshold.

"It’s hard to say at this point, but I still think it has an uphill battle," a GOP aide told Fox News Digital. "Especially given how many Democrats have expressed opposition to it — whether directly or indirectly."

Fox News' Jason Donner contributed to this report.