Sens. Ben Nelson (D-Neb.) and John Warner (R-Va.) have quietly entered into talks on the possibility of drafting a new bipartisan resolution addressing the Iraq War despite growing pressure from GOP and Democratic leadership to maintain party loyalty in the increasingly partisan debate, sources close to the issue said.

Across the Capitol, divisions remained as House Democratic lawmakers began to mull through details in a proposed $120 billion-plus Iraq War spending bill, although many rank-and-file lawmakers contend that debate over the measure has cooled significantly as it heads to the full Appropriations Committee on Thursday.

As of Tuesday evening in the Senate it was unclear how formal — or far — the talks between Warner and Nelson had progressed, and spokesmen for both lawmakers declined to comment. However, Warner has said he cannot support the Democrats’ latest Iraq proposal in part because of its hard timeline of withdrawing troops within a year, and Nelson also has expressed reservations with hard benchmarks in the past.

Although the possibility of a new Warner-Nelson bipartisan resolution appeared to catch senior leadership aides in both camps off guard, this is not the first time the two have collaborated on a politically sensitive issue despite expectations of fealty by their leaders.

Warner worked closely with Nelson in crafting his bipartisan anti-“surge” resolution last month, and while events on the ground have made that resolution moot it could provide a basic foundation for their talks. The two lawmakers also played key roles in the formation of the “Gang of 14” in 2005 that helped end the “nuclear” option standoff over President Bush’s judicial nominations.

With Republicans agreeing to move to Senate Majority Leader Harry Reid’s (D-Nev.) latest Iraq resolution today, a potential Warner-Nelson deal could play a role in either this week’s Iraq debate or the looming fight over the supplemental spending bill.

Reid and Senate Minority Leader Mitch McConnell (R-Ky.) have at least for now abandoned efforts to come to a bipartisan deal on Iraq and have shifted into much more aggressive stances for this week’s debate. Additionally, both leaders for weeks have been stressing the importance of party loyalty in the Iraq debate and have gone to great pains to try to convince the public their respective caucuses are united on their positions.

Both leaders have stepped up their political rhetoric, and aides on both leadership teams have indicated they are expecting a nearly party-line vote on Reid’s resolution, which would force a redeployment of forces in Iraq and put in place new limits on President Bush. A number of Senators, including Warner and Sen. Norm Coleman (R-Minn.), have indicated that while they may vote today to begin debate, they will oppose the resolution as it stands now.

According to a GOP leadership aide, while Republicans are largely unified in opposition to Reid’s proposal, there remain significant divisions on how to handle it procedurally, with some Members arguing for a straight up-or-down vote on the bill, while others would like to offer alternatives and still other Members hoping to postpone the debate altogether until the supplemental fight.

On the House side, meanwhile, Majority Whip James Clyburn (D-S.C.) said Tuesday that the whip team would begin counting votes on the Iraq spending measure, which is scheduled to be marked up Thursday by the Appropriations Committee.

“We will start counting this afternoon,” Clyburn said at a press conference on an unrelated subject. “But we are working the language right now to see exactly where we are.”

House Majority Leader Steny Hoyer (D-Md.) declined to speculate on current support for the measure, but stated at an earlier press briefing that Democrats are prepared to whip the bill: “We are going to be whipping it and counting votes, and I think we are going to get the vote.”

But a Democratic source said Clyburn actually is just taking an informal survey of support for the measure at this point and noted that no final decision has been made on whether to whip votes on the supplemental bill.

Rep. Maxine Waters (D-Calif.), co-chairwoman of the Out of Iraq Caucus, told reporters Tuesday that she will vote against the supplemental. “I’m very firm in my opposition,” she said, adding that the measure can not be “nuanced” to change her vote.

Waters is a Deputy Whip in Clyburn’s operation but said she would not be whipping in favor of the bill. She said she would not actively whip against it either. “I think my position is very clear,” she said.

While Deputy Whips are usually expected to toe the party line on major votes, Rep. G.K. Butterfield (D-N.C.), also a Deputy Whip, said he did not expect retribution for voting against leadership on this particular issue.

“Generally speaking” party loyalty is expected for Whips, he said, but because the war is largely viewed as a vote of conscience it would be harder to enforce party discipline in the whip operation on this vote.

Butterfield said Democratic leaders were still working to forge consensus on the massive war supplemental, but he was confident they would be successful once the bill hits the floor. “I believe it will pass,” he said.

Similarly, Waters credited leadership efforts to build consensus, even if they won’t be able to get her vote. “I think they’ve done the best job they could do,” she said.

Many Democratic lawmakers similarly acknowledged the massive bill’s imperfections — some liberal Members are disappointed in a decision to remove language prohibiting President Bush from expanding the war into Iran, while their conservative colleagues object to the inclusion of a timeline for withdrawal from Iraq — but asserted that the majority is moving toward a “critical mass” expected to approve the measure with a slim margin.

“It seems like we’ve gotten to a point where everybody understands it’s important to support the supplemental,” House Intelligence Chairman Silvestre Reyes (D-Texas) said after exiting the weekly Democratic Caucus meeting.

Rep. Jim McGovern (D-Mass.) characterized the meeting, which included a presentation led by Appropriations Chairman David Obey (D-Wis.), as “a healthy discussion,” adding it was noticeably less tense than in recent weeks.

Rep. Ellen Tauscher (D-Calif.), chairwoman of the centrist New Democrat Coalition, praised Democratic leaders for their ongoing efforts to meet with the Caucus’ factions.

“The Speaker deserves lots of plaudits for creating this working model of government that’s being established,” she said, adding that Democrats are moving toward the minimum number of votes need to pass the measure: “We’re building to 218.”

Although many rank-and-file Members said Tuesday they had yet to see a final draft of the spending bill — distributed only to members of the Appropriations panel thus far — based on the details provided by leadership, Democrats said they expected the measure would pass.

“I think we have the votes,” said Rep. Elijah Cummings (D-Md.), who acknowledged, “This legislation like most legislation isn’t perfect” but “I’m comfortable with it.”

Both Cummings and McGovern said they were disappointed by Democratic leaders’ decision to remove the Iran provision from the measure, but said the proposal is expected to return to the House in a stand-alone bill.

“Leadership has assured us there will likely be a separate vote on that at some point,” Cummings said. He added that the bill is expected to focus not only Iran but other nations as well.

In the meantime, however, many lawmakers, including leaders of the Progressive Caucus, declined to comment on the bill Tuesday, including Rep. Barbara Lee (D-Calif.), who stated she was reviewing the measure. In particular, members of the Progressive Caucus — who had pushed for full withdrawal by the end of 2007 — are concerned that the August 2008 withdrawal deadline proposed in the spending bill needs to be binding and enforceable.

“The Caucus is still split,” acknowledged one Democratic lawmaker, speaking on the condition of anonymity. “This is not going to be an easy sell.”

House Minority Whip Roy Blunt (R-Mo.) told reporters Tuesday that GOP members of the Appropriations Committee were meeting to discuss what amendments to offer during Thursday’s markup. Blunt said at the very least Republicans would offer language to strike the date-specific withdrawal and language that would allow President Bush to waive existing guidelines governing rest periods and training for troops currently included in the legislation which has sparked the most fierce opposition from his Conference and the White House.

Rep. Jerry Lewis (R-Calif.), ranking member of the Appropriations panel, also criticized non-military spending in the measure Tuesday, asserting Democratic leaders have weighted the bill in an effort to gain support for it.

“Instead, this legislation places military decisions in the hands of politicians and attempts to buy votes for its passage by promising something to everyone,” Lewis said in a statement. “It attempts to paper over Democrat divisions on the war in Iraq by delivering billions of dollars in unrelated and unauthorized spending that is somehow given an emergency designation.”

Citing additional spending for veterans’ health care, as well as funding for programs such as agriculture assistance to farmers, Hoyer defended those inclusions.

“We have provided for things that we believe are absolutely essential objects of expenditure and they were made necessary by the failure of Republicans in the last Congress to act responsibly,” Hoyer asserted.

Unless the bill is fundamentally altered before it hits the floor, however, Blunt reiterated that Republicans are nearly unanimous in their opposition. “I’m pretty confident,” Blunt said, adding that opposition was solid enough among the rank-and-file that it would not require a formal whip effort.

While Hoyer acknowledged the measure will need a majority of Democrats to succeed, he remained optimistic that some Republicans would cross party lines and support it.

“I think we’re going to have to do it primarily with Democrats,” Hoyer said. “I think we’re going to get some Republican votes, personally. I don’t know how many … but I think we need to expect that this is being made a political football.”

Susan Davis contributed to this report.