Don’t blink, because you might miss Congress passing a historic overhaul of the U.S. tax code.

House and Senate Republicans say they are nearing completion on a sweeping bill that would dramatically reduce the corporate tax rate, lower the top individual tax rate, nearly double the standard deduction, bolster the child tax credit and remove some breaks enjoyed by many Americans.

Members on Wednesday said a broad agreement has been reached between the two chambers that would address differences between their respective bills. Some issues, like small pay-fors, still need to be worked out, aides said.

Once final legislative text is available, expect it to move quickly.

Senate Majority Whip John Cornyn said his chamber would act first on a conference measure, with work to begin on Monday and a final vote possibly slipping to Tuesday.

Watch: Schumer Calls on McConnell to Delay Tax Vote Until Jones Is Seated

The full conference committee met Wednesday for what amounted to little more than a series of opening statements. Republicans praised the bill, while Democrats blasted the policy and the process the GOP used to advance it.

Sen. Robert Menendez, a New Jersey Democrat, called it a “big, fat wet kiss to corporations.”

Getting to a compromise

The real work was going on behind closed doors, as GOP leaders put the finishing touches on the bill that is expected to include limiting the mortgage interest deduction to debt of up to $750,000 and permitting pass-through businesses to deduct up to 20 percent of their income, according to GOP aides.

The compromise agreement, aides say, would also retain the popular deduction for medical expenses and repeal the individual mandate included in the 2010 health care law, among other provisions.

But there are some lingering issues that could complicate the Republicans’ aggressive timeline to pass the bill before leaving for the Christmas holiday break.

Some key constituencies in both chambers have yet to sign off on the agreement, though Republican aides are confident they will have the votes to advance the bill in the House and Senate.

“We’re going to have a very good package that we’ll be able to pass really quickly,” House Chief Deputy Whip Patrick McHenry said.

But not everyone is publicly on board yet.

Sen. Marco Rubio, for example, has expressed concerns about plans to reduce the corporate tax rate to 21 percent (higher than the 20 percent initially included in the House and Senate bills), while lowering the top individual tax rate to 37 percent.

The Florida Republican had previously called for raising the corporate rate to offset changes intended to boost the child tax credit. His goal to make the credit more generous has been embraced by top White House adviser (and President Donald Trump’s daughter) Ivanka Trump, who met with Senate Majority Leader Mitch McConnell on Wednesday to talk taxes.

“If the conference report does not make some improvement on the refundability [of the child tax credit], leadership knows where I stand,” Rubio said of the conference report.

When asked to elaborate, he said he was “not going to make public threats,” but said leadership was aware of his position.

House Freedom Caucus Chairman Mark Meadows said he’s optimistic that the tax deal is something conservatives could support. But the North Carolina Republican added that he’ll need to see more detail and his hard-line conservative group will have to meet to discuss it.

Other priorities

Republicans are hoping to pass the tax overhaul — the first in over two decades — before leaving town for what likely appears to be the remainder of the year. But prior to recessing, Congress must also address the upcoming Dec. 22 deadline to fund the government.

Members leaving a House GOP conference meeting Wednesday said the group discussed a variety of plans, including a combination bill that would include a continuing resolution until Jan. 19 with defense spending .

“The plan is to pass the CR with the Defense appropriations bill, which of course, will be stripped out by the Senate,” Pennsylvania GOP Rep. Charlie Dent said.

But Meadows said he doesn’t expect the CR to include a higher-defense spending level or a full-year Defense appropriations bill. When asked if his caucus members would vote for the CR if it doesn’t include defense, Meadows said, “It would be difficult.”

Aides from both parties expect the final product to be a CR that lasts until January.

Congressional leaders continue to negotiate the levels for new spending caps in fiscal 2018 and it is unclear where those discussions sit. Republicans say Democrats have refused to cooperate until work on the tax bill — which has been largely a partisan process — is over.

Lindsey McPherson, Jennifer Shutt and Kellie Mejdrich contributed to this report.