WASHINGTON — The Senate's No. 2 Democrat says if House Republicans follow through on threats to raise defense spending through the wartime account known as OCO, they can expect resistance from Democrats.

Assistant Minority Leader Dick Durbin, D-Ill., pushed back against House Armed Services Committee (HASC) Chairman Mac Thornberry’s assertion that $59 billion allocated for the Ooverseas Ccontingency Ooperations account (OCO), was considered a floor and not a ceiling by the two-year bipartisan budget deal reached late last year. Thornberry has said in recent weeks that last year’s budget deal clearly set the amount as a minimum to be raised based on current threats. 

"I viewed it as a ceiling, not a floor, but I would like to hear his explanation," Durbin said of Thornberry on Thursday. "There is one abiding concern: fifty-fifty, defense and non-defense."

A key principal for Democrats during last year's budget negotiations was that any increase for the defense side of the budget be matched equally on the non-defense side. Asked if Democrats would stick to that principal, should the GOP seek an OCO plus-up, Durbin told Defense News: "I will."

As Capitol Hill awaits the president's 2017 budget proposal Feb. 9, familiar lines are being drawn in a battle that threatens to undo the carefully crafted Bipartisan Budget Agreement of 2015 (BBA), a two-year deal that was supposed to provide stability to a budgeting process that has been irregular for most of President Barack Obama's administration.

Defense hawks in Congress looking to plus up increase the defense budget appear to face a four-way fight — with cCongressional Democrats, President Obama and fiscal hawks in their own party.

The House's fiscally conservative Freedom Caucus wants to spawn a politically explosive budget proposal that would restore Budget Control Act spending caps, eased by $30 billion for fiscal 2017 as part of the budget deal. Its members argue the country is on a fiscally unsustainable path and must make steep entitlement cuts to reduce rising deficits.

House Speaker Paul Ryan is already working to unify his caucus and avert a budget impasse a split among House Republicans. Rep. Tom Cole, a member of the budget and appropriations committees who has served as a Republican budget negotiator, said his party's disunity on the budget threatens to sink Congress back into the recurring nightmare of threatened government shut-downs and stop-gap funding measures.

"We certainly at this point don't have 218 Republican votes for a budget," Cole, R-Okla., said Thursday. "On the other hand, that deal was made, and I don't see how you break your word. … We've tried to give everybody in government, and certainly the military, a little bit more stability; the bleeding needs to stop and they need to have some budget certainty. Hopefully cooler heads will prevail."

Last year's budget fight ultimately yielded a deal that safeguarded the essential operations of the Treasury and the Pentagon but led to House Speaker John Boehner's resignation over fights against the Freedom Caucus.

This year, Speaker Paul Ryan will have to find his own way to deal with the group that bedeviled his predecessor. In remarks at the Heritage Action Conservative Policy Summit on Tuesday, Ryan suggested ambitions of his colleagues be scaled back as long as President Obama wields the veto, and he invoked the movie "Braveheart," saying "we have to unite the clans."

"When voices in the conservative movement demand things that they know we can't achieve with a Democrat in the White House, all that does is depress our base and in turn help Democrats stay in the White House," Ryan said. "We can't do that anymore."

Members don't appear to have budged. Rep. Dave Brat, a member of the Freedom Caucus on the House Budget Committee, said Thursday he hoped Budget Committee chairman, Rep. Tom Price, R-Ga., would produce a budget proposal that complies with BCA caps, and that Senate Majority Leader Mitch McConnell, R-Ky., would signal his support early — calling the whole thing "easy." 

"I won't support anything that busted the original caps," said Brat, R-Va. "There's an easy win-win, and that's to make a trade between the new, higher caps and a bold move on entitlement, mandatory, automatic spending. That's the easy move."

The other looming fight is Thornberry's stand to increase OCO if the Obama administration's budget sets it at $59 billion, as expected.

Defense Secretary Ash Carter, in a preview of the administration's $582 billion defense budget request, said the administration will request $59 billion for OCO, in line with the budget deal, but signaled he is also open to spending more, telling reporters during a trip to Naval Air Weapons Station China Lake, California Calif., that, "OCO is by definition a variable fund that depends upon what you do in the course of a year."

The 2016 defense policy bill avoided breaking the cap on base budget spending by shifting roughly $38 billion of the total requested for the defense base budget into the OCO account, which — while exempt from the budget caps — is intended to provide emergency funding for pop-up missions. The president, who objected to lifting the spending cap on defense without providing equal relief for non-defense discretionary spending, vetoed the policy bill in protest.

To resolve the impasse, the budget deal raised the discretionary spending caps for both defense and non-defense programs by $80 billion over two years, ultimately tucking around $8 billion for base budget activities into the OCO account.

Republicans initially included language in the budget agreement that which set $59 billion as the floor for OCO, but the language did not make it into the final draft, according to Mackenzie Eaglen, a former staffer both on Capitol Hill and in the Pentagon. She says the Hill’s intent in the agreement is clear nonetheless.

"The iterations of [budget agreement] basically were, before the final version, that it was a floor," she said. "You could argue that since it was taken out you can interpret it in black and white, but it's clear that is what was meant by Hill Republicans always, was that it was a floor."

Thornberry is not alone. Also on the side of raising defense spending are two staunch defense hawks in Senate Armed Services Committee, its chairman John McCain and Lindsey Graham, a military veteran and member of the SASC. McCain has proposed lifting the budget caps for defense alone, while Graham said Thursday he will press colleagues to boost the Pentagon's budget.

At the suggestion fiscal conservatives who want to lower budget caps might be an obstacle to those efforts, Graham offered a fiery rebuke.

"They're not very conservative, don't use the word conservative when you're talking about cutting the military," Graham, R-S.C., told reporters. "I don't want to hear one person say they're conservative if they want to go back to BCA numbers, regarding the military. What they are is extremists who have their heads in the sand and don't understand the world. If you think the BCA numbers are good for the Department of Defense, you are absolutely a fool."

Invoking the Islamic State group-inspired attack in San Bernardino, McCain, R-Ariz., warned Democrats off seeking equivalent spending on the non-defense side, should Republicans seek a defense hike.

"Even with an attack on the United States of America, they can't change," McCain said of Democrats. "National security is the number one or number two concern of the American people, and it's going to play out to their deep embarrassment if they block it. It's absolutely disgraceful. How many Americans have to die?"

McCain said he planned to coordinate with Thornberry on a response to the president's budget.

GOP Defense hawks in the House are already lining up to push for more funding, expressing agreement with Thornberry's assertion that OCO should be raised to reflect current threats.

Ahead of the president’s budget release, the GOP game plan for an OCO fight is not set, according to the chairman of the House defense appropriations subcommittee, Rep. Rodney Frelinghuysen, RD-N.J. However, Frelinghuysen said Thornberry has his support.

"We need an account with as much flexibility in it as possible, and that's something the commander-in-chief will need more of, rather than less," Frelinghuysen said Thursday. "I won't go to the numbers, but its a very important part of keeping us safe here at home and allowing us to address what I consider to be the cancer spreading across the Middle East and North Africa, represented by the Islamic State."

Assistant Majority Whip Rep. Joe Wilson, who serves as chairman of the HASC's emerging threats subcommittee, said Thornberry would likely receive Ryan's blessing and analytical support from House leadership's budget advisers.

"I will certainly be backing up the chairman to maintain what the agreement was, and the good news is we have a chairman who fully understood the agreement," Wilson, R-S.C., said Thursday "We always have to go to the speaker, but key budget advisers of the speaker have indicated that indeed Chairman Thornberry is correct."

Tactical Air and Land Subcommittee Chairman Mike Turner, who led efforts to plus-up the 2016 defense budget, was already rallying House Republicans to the battle lines on Wednesday, asserting the Obama administration "appears to be breaking from the agreement included in the Bipartisan Budget Act of 2015."

"The administration's disregard for the agreement jeopardizes our national security and deprives our military of the resources necessary to defeat evolving threats," Turner said in a statement to Defense News. "As the House prepares to consider a budget resolution for fiscal year 2017, members must remain committed to providing a robust national defense and advocate on behalf of our warfighters."

Aaron Mehta contributed to this report.

Twitter: @reporterjoe