When the Republican convention opens Monday night, its prime-time lineup could be missing one of its biggest draws: California Gov. Arnold Schwarzenegger.

Schwarzenegger is vowing to remain in California if lawmakers there fail to reach agreement on a state budget, now two months overdue.

"I made it very clear to Sen. McCain when I spoke to him yesterday and I made it very clear to his people that I am honored to be asked to speak at the convention ... and that I would be honored to do anything to help him win the presidency, but that the state of California and the budget is the most important thing," Schwarzenegger says. "So that if I don't have a budget, I cannot speak at the convention."

A budget deal by showtime seems unlikely at this point, potentially costing Schwarzenegger a national platform and McCain a high-profile supporter who has been popular with the kind of independent voter McCain hopes to attract.

Schwarzenegger's absence also would be a letdown for the TV networks, which would lose one of the biggest potential draws on the convention's opening night. Other speakers scheduled for Monday include President George W. Bush, Vice President Dick Cheney and numerous members of Congress.

Schwarzenegger's failure to commit is proving to be a source of frustration for convention organizers, who like to nail down their programs well in advance. Given the star power of the actor turned politician, they'll still squeeze him into a prime slot if they can get him.

The stalled budget already forced Schwarzenegger to curtail nearly all appearances this summer. His efforts to cajole lawmakers into a compromise have repeatedly fallen flat.

California is the only U.S. state with a fiscal year beginning July 1 that has not approved a spending plan.

Lawmakers remain at odds over how to close a $15.2 billion budget gap, with Republicans adamantly opposed to any tax increases and Democrats seeking to avoid massive program cuts.