Gov. Arnold Schwarzenegger will not decide whether to comply with President Bush's plan to put National Guard troops on the Mexican border until he gets more information, the governor's office said Wednesday.

Schwarzenegger aired his concerns in a telephone call with Homeland Security Secretary Michael Chertoff on Wednesday afternoon.

"Following the 40-minute conversation, it was clear the administration didn't have the answers," said Schwarzenegger's spokeswoman, Margita Thompson.

Bush is asking governors to comply voluntarily with his plan by sending National Guard troops. But if a governor were to refuse, the president could federalize Guard units and send them himself.

On Tuesday, Schwarzenegger made public a letter he sent to Chertoff that questioned how the Bush administration plans to use the Guard. He asked what the government believes would constitute a successful border deployment and when it might end.

He also said that putting Guard units at the border for two- to three-week rotations would be "a logistical nightmare" and would be asking too much of troops who had recently returned from Iraq and Afghanistan.

For a Republican governor, Schwarzenegger has been unusually vocal in his criticism of Bush's plans. Schwarzenegger said he supports Bush's goal of reducing illegal immigration but does not think using the Guard is the right way to do it.