As talks stalled Wednesday, Members of Congress on the payroll tax cut conference committee began to acknowledge that negotiations might have to go behind closed doors for any real work to get done.

Senate Democrats met off-campus at their private annual retreat attended by President Barack Obama. Republican conferees, meanwhile, huddled in House Ways and Means Chairman Dave Camp’s office for about an hour.

“We had a good meeting and we’re working through issues, but it’s kind of hard to make much progress until we get a proposal from the Senate,” the Michigan Republican said.

Most of the contentious issues surrounding the extension of a payroll tax holiday and a lapse in Medicare payments to doctors remained unsettled, and Republican conferees said they were still awaiting an offer on unemployment insurance issues from Senate Finance Chairman Max Baucus (D-Mont.).

That offer is expected to come today and will likely address the most controversial unemployment insurance issues, such as the number of weeks to pay out benefits and GOP-favored requirements that jobless beneficiaries be tested for drugs. Members and staff were tight-lipped about the specifics of any offer Wednesday.

Members had been told to keep their schedules open this morning, but as of press time, Camp, co-chairman of the conference committee, had not decided whether a meeting would occur or whether any potential meeting would be open to the public.

House Energy and Commerce Chairman Fred Upton (R-Mich.) had some cause to think Members could make more headway if the talks were out of the public eye.

“We haven’t had any progress with them being in public, so maybe if we do one private meeting, we can actually make some progress,” he said.

But despite Upton holding that there have been “very few private discussions going on,” he said progress has been made toward an agreement to sell telecommunications spectrum as an offset to a potential package.

“We had a $16.5 billion pay-for as part of that [House-passed bill], and I think we’re getting pretty close” to that number, Upton said. “We’re meeting with the Democratic staff, and [having] some Member discussion, and we really have made some progress.”

Conferees said progress has also been made on settling minor unemployment insurance issues, such as a requirement that states recover overpaid jobless benefits and a mandate that those who receive benefits seek re-employment, two items in the House-passed bill.

Yet the unemployment insurance issues don’t get to the heart of the partisan disagreements, and the spectrum offset is just a drop in the bucket toward paying for the whole package.

Energy and Commerce ranking member Henry Waxman said he agreed that with an end-of-month deadline, conferees might have to meet privately to hash out a deal.

“The meetings have been productive, but it’s time to move now to another stage,” the California Democrat said. “Now that we’ve stated our positions clearly, albeit sometimes with passion, we have to recognize that we have to reach common ground and get this legislation passed.”

Sen. Bob Casey echoed the sentiment a day earlier, telling reporters after Tuesday’s conference committee meeting that he has had some Member-to-Member discussions and would like to have more private talks.

“If all we’re going to do is have a very formal process, I think we’re limiting ourselves,” the Pennsylvania Democrat said. “I think that’s important, to have those [one-on-one] discussions to try to better understand what the other side is proposing or what’s preventing them from agreeing with you.”

Still, the conferees are under a tremendous amount of pressure, and leadership on both sides seems innately distrustful that the other wants to strike a deal.

Speaker John Boehner (R-Ohio) indicated Tuesday that he thinks Senate Majority Leader Harry Reid (D-Nev.) might be slow-walking a proposal, a sentiment that conferee Rep. Tom Reed (R-N.Y.) echoed Wednesday.

Reed said Democrats think they can put political pressure on Republicans by moving slowly.

“Maybe there’s a calculation that’s been made on their side, from a political point of view, that they come out better,” he said. “I was hopeful coming over here today that I would hear that the Senate had put that [unemployment insurance offer] in writing and delivered that to us. We have yet to hear a response to that, even just a position as to where they stand on UI.”

Meanwhile, including a provision to spur the construction of the Keystone XL pipeline in a payroll package seems almost an afterthought. Republicans pushed hard to include it at first, but the Energy and Commerce Committee passed a Keystone XL bill Tuesday that would place the Federal Energy Regulatory Commission in charge of granting the permit.

Still, Sen. John Barrasso (R-Wyo.), a conferee, said he will keep pushing for the project.

“I’d like to see it in anything that goes to the floor,” he said.