President Obama placed his political capital on the line Monday and reiterated his threat to veto a military spending bill unless the Senate removed $1.75 billion set aside to buy seven additional F-22 fighter jets.

Mr. Obama stepped up his campaign after liberal Democrats like Senators Edward M. Kennedy and John Kerry of Massachusetts said they supported the purchases, arguing that the program would retain high-paying jobs in many districts nationwide.

The F-22, the world’s costliest fighter jet, is the most prominent weapons system that Mr. Obama wants to cancel or cut in his plan to rein in military spending. A vote by the Senate to keep producing the plane would be an embarrassing setback for him.

Military analysts say it has always been hard to persuade Congress to halt big weapons programs like the F-22, made by Lockheed Martin, which has suppliers in 44 states and provides 25,000 jobs.