At around 7:30 p.m. ET, the Senate is slated to vote to break a filibuster on the agreement to raise the debt ceiling, which needs 60 votes to succeed.
Top Republicans have projected confidence that enough of their members will vote with Democrats for the measure to clear the procedural hurdle, but some Republican senators have said they are not sure if the votes are there.
If that vote succeeds, the Senate will vote on final passage, which requires only a simple majority.
If the Senate approves the debt limit extension, the House will next have to approve it before it can be sent to President Joe Biden for his signature.
Senate Majority Leader Chuck Schumer announced that a deal had been reached on Thursday morning. An aide familiar with negotiations told CNN that the deal Schumer announced is to increase the ceiling by $480 billion, which is how much the Treasury Department told Congress it would need to get to December 3.
Both parties have made clear that the country must not default and that even coming close to it would likely bring catastrophic economic consequences.
Yet while the deal announced Thursday stands to avert immediate economic disaster, it does not resolve the underlying partisan stalemate over the issue. It merely delays the fight until another day.
That fundamental dispute remains, making it unclear what will happen in early December.
House Speaker Nancy Pelosi has indicated that members may need to come back to vote on the measure if it passes the Senate.
“At this writing, the Senate is engaged in hours of debate that will lead to a vote to lift the debt ceiling,” she wrote in a letter Thursday evening, adding, “Hopefully that will occur and if it is necessary for Members to return early, Leader Hoyer will give sufficient notice as promised.”
McConnell said on Thursday that the agreement provides Democrats with more time in the next two months to use reconciliation to raise the debt limit themselves.
He argued this resolves the “the majority’s excuse that they lacked time” to address it through the cumbersome budget process.
McConnell again repeated his other so-called compromise that Republicans would be open discussing a longer term bipartisan debt ceiling increase, if Democrats ditch their massive social safety net bill. That would be a non-starter for Democrats, however.
“If our colleagues would instead prefer a more traditional bipartisan discussion around basic governance, they can stop trying to ram through yet another reckless taxing and spending spree. … That would be the path toward that kind of discussion,” he said.
Treasury Secretary Janet Yellen had warned lawmakers that the federal government will likely run out of cash by October 18 unless Congress raises the debt ceiling.
But Congress may not even have that long, since the deadline is more of a best guess estimate than a set in stone deadline. That dynamic intensified pressure on both sides to reach a deal this week.
This story has been updated with additional developments Thursday.
CNN’s Manu Raju, Lauren Fox and Ted Barrett contributed.