With a government shutdown approaching, House Republicans may try to force Senate Democrats into a corner on year-end legislation by bringing an omnibus spending bill to the floor Friday and daring them to oppose it.

The move would be an attempt to undercut Democrats’ strategy of refusing to formally sign off on the spending bill until Republicans and Democrats can reach agreement on an extension of President Barack Obama’s payroll tax holiday.

As House Republicans contemplated their next steps, Senate Democrats appeared poised to offer a payroll tax deal in which they would drop their insistence on a millionaires’ tax in exchange for the GOP agreeing to abandon its push for a controversial oil pipeline, among other things.

House GOP appropriations conferees have signed off on the omnibus conference report, Republicans say, and are waiting for their Democratic counterparts to do so.

Democrats have said there are still outstanding issues to be resolved before the spending deal is final.

At a two-hour Republican Conference meeting Wednesday, Members discussed voting on a stand-alone bill that mimics the conference report to which they say Democrats have already agreed.

House Appropriations Chairman Hal Rogers (R-Ky.) predicted after the meeting that the chamber could pass the new spending measure and send it to the Senate before the current federal funding runs out Friday.

“We would pass the bill, send it over there; that should end it,” he said. “That’s on Friday, and the deadline is Friday night, and the Senate has a chance to stop a government shutdown.”

About 30 Members spoke in the meeting, including Republican Study Committee Chairman Jim Jordan (Ohio), who spoke in support of forcing the spending bill to the floor, according to sources in the room. To comply with their three-day rule in the “Pledge to America,” Republicans would have had to file such a measure before midnight Wednesday.

Exiting the meeting, however, Speaker John Boehner rebuffed questions about whether he would bring the bill to the floor. The Ohio Republican instead said the Senate should not hold up the appropriations bills in order to extract concessions on a House-passed package, including a payroll tax cut extension and other measures.

“I’m tired of hearing what the Senate can’t do,” Boehner said. “The House has done its work. It’s time for the Senate to do theirs. We’ve got an agreement in a bipartisan way on the appropriations process to fund the government. There’s no reason for it to be held hostage to give leverage to one side or the other.”

Democrats have found themselves suddenly on the defensive on the payroll tax cut — an issue they had dominated early but for which momentum has since shifted to Republicans after they successfully made the Keystone XL pipeline part of the conversation. They also have been helped by Senate Majority Leader Harry Reid’s decision to link it to the appropriations process.

Indeed, the Nevada Democrat and his entire leadership team were summoned to the White House on Wednesday afternoon for a hastily arranged meeting with President Barack Obama to discuss the situation.

Following the meeting — which Conference Vice Chairman Charles Schumer (N.Y.) described as “very nice” — Democratic leaders said they were still no closer to resolving the standoff.

For instance, while Majority Whip Dick Durbin (Ill.) told reporters that “the president is still concerned” with some of the policy riders and other aspects of the spending and payroll bills, Reid said “there’s a lot of issues we’re working through.”

Part of the problem, Democrats insist, is the fact that Senate Minority Leader Mitch McConnell (R-Ky.) has thus far been unwilling to let Reid bring the House’s payroll tax bill to the floor for a quick vote and all but certain defeat.

With Boehner waiting for the Senate to demonstrate it will not accept the House version before entering into talks on a compromise, Democratic aides insisted McConnell is essentially stalling any progress toward resolving the impasse.

In an apparent attempt to get Republicans back to the negotiating table, Democrats began to signal Wednesday that they may be willing to drop their demand for a tax on those making more than $1 million a year in return for concessions by Republicans. The development came after the Senate leadership meeting at the White House.

The protracted staring contest between Republicans and Democrats — a practice that has become commonplace in the lead-up to holiday breaks or long recesses, particularly when the issue is spending — has further eroded the already battered comity on Capitol Hill.

Reid and McConnell engaged in a particularly terse exchange on the Senate floor Wednesday morning when McConnell blocked Reid’s effort to bring the House bill to the floor.

When Reid rejected McConnell’s proposal to allow the vote only if he agreed to vote on the omnibus spending bill, the Republican leader attacked Democrats.

“Here we are a few days before Christmas and the silliness continues,” McConnell said during his floor exchange with Reid. “If my friend the Majority Leader is so convinced that the House-passed [payroll] bill can’t pass the Senate, I would say again, talk to [Boehner] and work out something that can pass both the House and the Senate. Time is wasting.”

Reid then fired back, suggesting the partisan rhetoric was more about the 2012 presidential election than about legislating.

“Talk about a diversion. That’s what we just heard,” Reid responded. “My friend, the Republican leader, has talked from the very beginning of this Congress, his No. 1 goal is to defeat [Obama] for re-election. That’s not looking so good.”

But by the evening Reid, McConnell and Boehner were meeting privately.

The White House stepped up its efforts to pressure Republicans to agree to an “acceptable” spending bill. In a largely theatrical move, federal agencies Wednesday began the process of preparing for a shutdown, sending email “alerts” to employees to warn them of a potential shutdown.

And in a statement, Office of Management and Budget spokesman Kenneth Baer said Wednesday, “there is no reason for the government to shut down. Congress can avoid a shutdown by passing an acceptable omnibus spending bill as well as an extension of the payroll tax cut and unemployment benefits — or by passing another short-term CR as Congress has done seven times already this year.”

Baer also sought to legitimize the shutdown “preparations” under way within the administration, saying, “We do need to be prepared for any contingency, and in case Congress does not act, we are taking the steps necessary to be prepared if a lapse in funding should occur. That is why agencies are sending emails to their employees to alert them to this possibility and how it would affect them.”

David M. Drucker and Jessica Brady contributed to this report.