It's not every day that a president threatens to veto his own defense spending bill. 

But that's the rare position President Obama finds himself taking after senators made an 11th hour addition of $1.75 billion to buy seven F-22 fighter jets whose price tag has ballooned to about $350 million apiece. 

The fifth generation fighter jet has been overtaken by the newer F-35, critics argue, and Obama wants to keep with the recommendation of former President George W. Bush and cap the purchase at 187 jets. 

The president's not alone in opposing the change. He's also got the Democratic chairman of the Senate Armed Service Committee, Sen. Carl Levin, and his former GOP rival Sen. John McCain -- a war hero himself -- on his side. 

But with jobs on the line, other senators are putting up a fight for the F-22. 

Sen. Saxby Chambliss, R-Ga., whose state would lose at least 2,000 jobs should the cap be imposed, pushed for the seven extra F-22's to be built.

"While the administration is emphasizing winning current conflicts, its stance regarding the F-22 does not adequately account for other kinds of threats," Chambliss said. 

But the F-22 requires 30 hours of maintenance for every hour of flying time and costs the taxpayer about $44,000 an hour to fly, according to confidential Pentagon test results. 

"This plane has never flown over Iraq or Afghanistan -- the two wars that we are in," McCain said. 

Defense Secretary Robert Gates and Adm. Michael Mullen, chairman of the Joint Chiefs of Staff, wrote to senators Monday to express their dismay at the 11th hour addition. 

"We strongly believe that the time has come to close the F-22 production line. If the Congress sends legislation to the president that requires acquisition of additional F-22 aircraft beyond fiscal year 2009, the secretary of defense will strongly recommend he veto it," the letter said. 

Gates earlier said the insertion of more money, into the already $680 billion defense budget, for F-22s posed a "big problem" for him. 

Analysts say it would be unprecedented for a defense secretary and chairman of the Joint Chiefs to urge the president to veto their own defense bill. 

But they, and Obama, have made clear that they view such expenditures as wasteful. 

"We do not need these planes. That is why I will veto any bill that supports acquisition of F-22s beyond the 187 already funded by Congress," Obama said in a letter Monday to senators. 

Meanwhile, another last-minute potential showdown is brewing that could stall the defense bill. 

Sen. Kirsten Gillibrand, D-N.Y., told FOX News she plans to introduce an amendment Tuesday that would halt the enforcement of "Don't Ask, Don't Tell" legislation for 18 months. 

"We are losing some of the best and the brightest when we need them. We have two wars, we have Afghanistan, we have Iraq, we have missions all across the world right now that need the best and the brightest, and I think we shouldn't be limiting ourselves," Gillibrand said. 

The amendment would halt the Defense Department from removing any openly gay members of the military from serving for the next 18 months while the administration and the Pentagon review the policy.