WASHINGTON — The House Armed Services Committee's defense policy bill, passed April 28, tees up clashes with the Senate and the Pentagon, chiefly over a plan altering the use of the wartime overseas contingency operations (OCO) account.

Top-line funding for the DoD in the House's authorization bill hews to the top line for defense in the bipartisan budget deal, but reallocates $18 billion in war funding for personnel and big ticket weapons programs cut by the administration's request. It also leaves overseas operations funded only through April, a tactic that banks on the next president requesting Congress approve supplemental war funding to finish out the year.

Defense Secretary Ash Carter made clear the Pentagon will put up a fight over the plan, publicly lambasting the HASC language as "gambling" with troops' funding at a time of war, calling it "deeply troubling" and "flawed."

"I just want to highlight the danger of underfunding our war effort, gambling with funding for our troops in places like Iraq and Syria," Carter said. "As secretary of defense, I cannot support such a maneuver."

Carter is not wrong, according to former DoD Comptroller Bob Hale, who said it will take time for the next administration and Congress to advance the supplemental, which as must-pass legislation will likely attract "a lot of extraneous riders." A late bill would mean the Pentagon would have to scramble to reshuffle funding to ensure vital overseas operations are not derailed.

"Will they pass it eventually, I suspect they will, but it's a lousy way to run a railroad," said Hale, now a BoozAllen Fellow.

The secretary earned a quick response from a top HASC Republican when House Armed Services tactical airland subcommittee Chairman Mike Turner, R-Ohio, shot back that Carter has "lost total credibility" on budget matters.

Carter's comments were clearly aimed at driving the members of the two Senate committees to block the House plan, and could be early signaling to Congress that he would recommend President Barack Obama veto any bill with such OCO language.

The good news, for Carter, is that Senate Armed Services Committee Chairman John McCain, R-Ariz., had indicated he wants to approach OCO funding differently from the House. The SASC is expected to take up its authorization bill May 11.

Aside from the OCO issue, Turner predicted the NDAA's policy provisions barring the closure of the detention center at Naval Station Guantanamo Bay, Cuba, might bait a presidential veto threat.

Speaking on background, a senior defense official said a potential veto will be discussed "within the context of the entire bill. There is a formal process associated with that."

However, the fight between Carter and the House is just a sideshow to the much larger fight brewing between Senate Democrats and Republicans — one that may end up with the Pentagon funded, once again, under a stop-gap continuing resolution.

The Senate is in turmoil following an amendment introduced to the Energy and Water appropriation bill by Sen. Tom Cotton, R-Ark., that would ban the US from using government money to buy Iranian heavy water, used in nuclear reactors.

The purchase of that water is a key component of the Iranian nuclear deal, and Cotton's amendment is seen as a shot at the Obama administration over the controversial agreement. Senate Democrats have made it clear that they will not allow the amendment to come to the floor for a vote.

Mackenzie Eaglen of the American Enterprise Institute sees the Senate blockage over the Cotton amendment as something that was inevitable. The only question, she says, was what would cause it.

"Ultimately, the CR is coming. But it will not be because of the HASC budget gimmick," she said. "And all senators already know this. The only people who don't are Carter and the House."

The Senate will likely put up a fight about another provision in the HASC bill, which gives the Air Force leeway to procure extra RD-180 rocket engines, a Russian design that is the backbone of the service's military space launch.

McCain has made it clear he wants the Air Force off the Russian engines as quickly as possible and has rejected past calls from the service to give them the ability to buy more engines.