Gov. Arnold Schwarzenegger this week rejected a request from the Bush administration to send an additional 1,500 National Guard troops to the Mexican border, the governor's office confirmed Friday.

The National Guard Bureau, an arm of the Pentagon, asked for the troops to fill shortfalls for the mission in New Mexico and Arizona, two California National Guard officials told The Associated Press on Friday. But Schwarzenegger said the request would stretch the California guard too thin if an emergency or disaster struck.

The overall deployment for the border mission would remain at 6,000, the guard officials said, speaking on condition of anonymity because the request had not been announced by the military.

Col. David Baldwin, director of planning and operations for the California National Guard, would not comment when asked about the request from the White House. But he said because of the size of the state's Guard — which tops 20,000 troops — California is expected to have an easier time than other border states filling the request.

He said the state already has 250 troops on the border and between 400 and 700 of its promised 1,000 troops on orders to deploy.

"Other states that have smaller national guards are harder-pressed and may have to rely on other states," Baldwin said.

Schwarzenegger's communications director, Adam Mendelsohn, said the governor felt sending more troops was an inappropriate burden on the state and would disrupt the guard's training schedule.

On June 1, Schwarzenegger agreed to send the California National Guard to the Mexican border to help the federal government's effort to control illegal immigration. That ended a 17-day standoff with the Bush administration over whether the state would join the border patrol effort and who would pay for it.

California has committed to putting 1,000 troops on the border by July 31 and has 250 there already.

Schwarzenegger initially criticized the administration's plan to deploy troops to the border, saying it was the wrong approach to dealing with illegal immigration.

The governor finally relented after the Pentagon signed a document promising to pay for the entire mission, a cost that could top $1.4 billion nationally. Schwarzenegger also wanted the Bush administration to commit to a firm end date. It did not, but Schwarzenegger signed an executive order saying he would not authorize the deployment beyond the end of 2008.

Schwarzenegger also said he intends for the mission to be carried out mostly by troops who volunteer for the assignment.

That differs from the Bush plan, which called for putting Guardsmen on border duty instead of their annual two- and three-week training exercises. Schwarzenegger said that arrangement would have created severe logistical problems.