By Lauren Fox and Manu Raju, CNN

(CNN) -- A spending deadline, a potential Presidential veto and a bipartisan group of lawmakers hoping to finally unveil legislation that guarantees millions of Americans won't lose unemployment benefits at the end of the month.

Congress is up against clock, which means it's going to be a consequential and, yes, messy week on Capitol Hill.

This is the week things either finally come together or they fall apart for good on the stimulus.

Aides and members spent the entire weekend trying to close out outstanding issues from food stamp benefits to state and local funding. Lawmakers spent Sunday afternoon on an hours-long Zoom call. And while aides on both sides of the aisle agree a lot of progress was made, the bipartisan group still isn't finished with writing its bill. Sen. Joe Manchin, a Democrat from West Virginia, said last week that bill text would be out Monday. We'll see about that.

Later on Monday morning several sources told CNN that almost certainly isn't going to happen by the end of the day.

That's because there are still some significant sticking points -- namely lawsuit protections for businesses and workers that Republicans are demanding and aid to state and local governments that Democrats have been seeking.

The thinking among the bipartisan group is that they either cut a deal on both issues, or both of them fall by the wayside and they try to advance the other measures which they can agree on.

The group is trying to put together a detailed outline that could be unveiled later on Monday.

Remember

Even if the bipartisan group of lawmakers from the House and the Senate reach an agreement among themselves, that doesn't mean it's the end of talks. This has largely been seen as a starting point for leadership. Senate Majority Leader Mitch McConnell hasn't committed to putting anything on the floor. And House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer were careful in their endorsement of this process last week that this is a starting point.

Expect to see some summaries rolled out as early as Monday, but aides say there still isn't complete agreement on the two issues that have flummoxed leadership and negotiators for months: state and local funding and liability insurance.

First, state and local funding: Right now, lawmakers are very close on this issue. They're eyeing $160 billion for state and local funding that would be based on two factors. The first would be based in part on population. The second would be based on states and localities demonstrating a loss in revenue. The tentative framework right now would cap the amount of money any state can get. The reason for that is Republicans don't want this program to become a major slush fund for Democratic states like New York of California, which they argue were having problems with budget shortfalls long before Covid-19 hit.

Liability insurance: This has been THE issue for McConnell since the late spring. And as aides and members tried to iron out a middle ground over the weekend, it became clear just how hard it is to find one. Republicans have been backchanneling potential proposals with GOP leadership, but there still isn't an agreement. It's the issue that is proving the most difficult to solve.

Still not part of the proposal: Stimulus checks: Aides familiar with the negotiations tell CNN that despite the progressive push Friday for $1,200 stimulus checks to be included in the bipartisan framework, they still aren't going to be included. The reason is that negotiators estimate they'd cost anywhere between $300 and $500 billion, depending on who would qualify for them, and that's a significant amount of money that would turn a $908 billion economic relief package into a $1.2-$1.4 trillion one.

Keeping the cost of this package below $1 trillion is critical to garner Republican support. Democrats negotiating this package know that. So while they might lose Independent Sen. Bernie Sanders of Vermont, the hope is they can win over more Republicans to make up for it. They also are fully aware that tweets from Reps. Alexandria Ocasio-Cortez of New York and Rashida Tlaib of Michigan assailing their bipartisan framework might help them convince Republican senators the proposal is actually in the middle.

About that spending deadline

The government runs out of money on December 11. After this weekend, there still isn't an agreement on the omnibus. Aides on both sides acknowledge that the likelihood is that Congress will have to pass a continuing resolution to fund the government for an additional week while they finish their negotiations. Passing a one-week CR should not be that complicated.

However, it could complicate the stimulus. The only way that a stimulus package passes Congress is if it is attached to the omnibus. With those talks dragging out another week, the bipartisan stimulus talks could also drag out, too.

It's still important members find as much of an agreement as they can in the next few days, but an additional week does buy them more time. It can also buy them more trouble. The first rule of Congress is when you have the votes, you vote. The longer a bipartisan agreement languishes under public scrutiny, the longer people notice what they are or aren't getting as part of a deal and the higher the chances are that you lose votes.

"It's more time for people to get cold feet," one aide who has worked on the negotiations told CNN. "Sooner we can get it out the door, the better."

Some fireworks this week

The House is expected to vote Tuesday on the National Defense Authorization Act, a bipartisan defense policy bill that has been signed into law for 59 straight years. The Senate will vote sometime after that.

But while the $740 billion bill includes pay raises for America's soldiers, modernizations for equipment and provisions to require more scrutiny before troops are withdrawn from Germany or Afghanistan, President Donald Trump has threatened to veto the proposal.

If he does, the question becomes can Congress override that veto. House Majority Whip Steny Hoyer has said he's confident he'll have two-thirds majority in the House to override. In the Senate, many Republicans senators have signaled they'd vote to override. But this is going to be a major moment to watch. Trump is threatening to veto the bill because it didn't include a repeal of Section 230, a law that shields internet companies from being liable for what is posted on their websites by them or third parties. The bill also includes provisions to limit how much money Trump can move around for his border wall and another that would require the military to rename bases that were named after figures from the Confederacy.

The bill is a rebuke of some of Trump's most fervent promises and policies. But the vote to override would come as Trump is about to no longer be President.