It was the latest move by the Pentagon to cope with the strains of fighting two wars simultaneously and maintaining a higher troop level in Iraq as part of President Bush's revised strategy for stabilizing Baghdad.

"This policy is a difficult but necessary interim step," Gates told a Pentagon news conference.

For Hawai'i-based soldiers, the move means that more than 7,000 Schofield Barracks soldiers who left O'ahu in July and

August for a yearlong deployment to northern Iraq will have their stay extended.

Schofield officials last week announced a 46-day extension for about 1,000 soldiers with the 25th Special Troops Battalion, including the division headquarters and Tropic Lightning band. Those soldiers will now be coming home in September.

Gates said the Pentagon's decision to extend tours did not affect the Marines, whose standard tour is seven months, nor the Army National Guard or Army Reserve, which will continue to serve 12-month tours.

Gates said the new policy also seeks to ensure that all active-duty Army units get at least 12 months at home between deployments. He said it would allow the Pentagon to maintain the current level of troops in Iraq for another year, although he added that there has been no decision on future troop levels.

Some units had already been extended beyond 12 months by varying amounts. The new policy will make deployments more equitable and more predictable for soldiers and for their families, Gates said.

"I think it is fair to all soldier that all share the burden equally," he said.

Officials on Monday said some 13,000 National Guard troops were receiving orders alerting them to prepare for possible deployment to Iraq — meaning a second tour for several thousand of them. Officials said a final decision to deploy the four infantry combat brigades later this year will be based on conditions on the ground and named specific Guard units based in Arkansas, Indiana, Oklahoma and Ohio.

The Pentagon said the Guard units would serve as replacement forces in the regular troop rotation for the war, and would not be connected to the controversial military buildup that was ordered by President Bush and which officials say is starting to show some success in curbing violence in Baghdad.

Word has also emerged that Defense Department officials were considering a plan to extend by up to four months the tours of duty for as many as 15,000 U.S. troops already in Iraq as a way to maintain the buildup past the summer.

There are currently 145,000 U.S. troops in Iraq, and when the buildup is completed by June, there would be more than 160,000, officials are calculating.

Defense Department spokesman Bryan Whitman said today that with the way the rotation schedule is laid out now, the force size would begin to fall after August unless some action is taken — sending some troops earlier than expected or keeping some beyond their planned homecomings.

He declined to confirm details of any of the options under consideration.

"What you're hearing from various people are different ideas that are being looked at," Whitman said.

He also said no decision has been made to maintain the buildup after August, but others have said that they expect or want to keep the level that high through the year and possibly until February.

"There are any number of planning scenarios that the department is looking at that would address things such as how long you would maintain" the buildup, Whitman said.

"Some would keep the ... force level essentially the same," he said. "Some scenarios have it going up, some scenarios have it going down."

Meanwhile, an Iraqi government spokesman, Ali al-Dabbagh, cautioned against "premature" withdrawal of U.S. troops, saying that would create an opportunity for Iran and the al-Qaida terror network to make inroads in Iraq.

Al-Dabbagh, asked at news conference at the United States Institute for Peace in Washington about congressional efforts to force a pullout of U.S. combat troops, said, "They should finish the job."

He said no Iraqi wants U.S. forces to stay a long time, but "there is a job to be done." With Iraq's approval he said some troops could be safely withdrawn later this year or early in 2008.

But, he said, "the premature withdrawal of American troops will create a vacuum" and "Iran is a danger and al-Qaida is a danger."