President Bush's planned deployment of National Guard troops to the Mexican border would last at least two years with no clear end date, according to a Pentagon memo obtained Friday by The Associated Press.

The one-page "initial guidance" memo to National Guard leaders in border states does not address the estimated cost of the mission or when soldiers would be deployed. But high-ranking officials in the California National Guard said they were told Friday that deployments would not begin before early June.

While the military document makes clear the troops would remain under the command of their governors, it also indicates a high degree of federal control over operations. It states that the National Guard Bureau's Army and Air Directories "will serve as the states' focal points for force-planning, training, organizing and equipping their forces."

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Guardsmen in "all other states, territories and the District of Columbia" will serve a supportive role, according to the memo.

California Gov. Arnold Schwarzenegger, who has not yet decided whether to commit troops to the mission, led a conference call with the governors of Arizona, New Mexico and Texas to discuss the memo along with other issues concerning the president's plan.

"There still remains a lot of unanswered questions that the governor is concerned about," Adam Mandelsohn, Schwarzenegger's communications director. "Most specifically, the outstanding funding issues and whether there is a commitment to the two-year time frame," he said.

Texas Gov. Rick Perry and Arizona Gov. Janet Napolitano said they would support the deployment of National Guard troops to the border, while New Mexico Gov. Bill Richardson, a Democrat, has been more critical of the plan.

A spokeswoman for Perry said the governors agreed to send a letter asking the Bush administration to clarify issues such as funding, rotation and troop levels that would be stationed in each of the states.

Napolitano is more concerned about Arizona being reimbursed by the federal government, said Dennis Burke, a Napolitano co-chief of staff. "Our concern is the check in the mail."

The president outlined his plan Monday night as part of a national address on curbing illegal immigration, pledging to gain control of the border and give up to 12 million illegal immigrants a chance at citizenship.

He proposed deploying 6,000 troops at a time to the border in two-week rotations. The deployments would be temporary, he said, until enough Border Patrol agents were hired to secure the mission. He asked Congress to add 6,000 more Border Patrol agents by the end of his presidency.

The White House also said the troops would be financed with part of the $1.9 billion requested from Congress this year to supplement border enforcement.

The memo sent Friday to Guard leaders went further, stating that units would remain in a "federally funded" mission for "up to one year, with a force reduction to 3,000 during the second year."

The document described an "end date" for the mission when the U.S. Border Patrol operation "gains independent operational control of the (southwest border) and National Guard forces are no longer required for this mission."

The memo said the Guard units' missions will focus on "surveillance, reconnaissance, aviation, intelligence, engineering, training, vehicle dismantling, linguistics ... transportation and logistics."

They will not be asked to perform law-enforcement functions, but rather provide "vetted and pre-coordinated support to law enforcement."