It might take as long as half a century before U.S. troops can leave the volatile Middle East, according to retired Army Gen. John Abizaid.

"Over time, we will have to shift the burden of the military fight from our forces directly to regional forces, and we will have to play an indirect role, but we shouldn't assume for even a minute that in the next 25 to 50 years the American military might be able to come home, relax and take it easy, because the strategic situation in the region doesn't seem to show that as being possible," Abizaid said Wednesday at Carnegie Mellon University.

Abizaid, the former commander of U.S. forces in the Middle East, stepped down in March as the longest-serving commander of U.S. Central Command. He retired from the Army in May and now is at the Hoover Institution at Stanford University.

The rise of Sunni extremism, burgeoning Shiite extremism, the Arab-Israeli conflict and the world economy's dependency on Mideast oil will keep Americans in the Middle East for a long time, he said.

"I'm not saying this is a war for oil, but I am saying that oil fuels an awful lot of geopolitical moves that political powers may have there," Abizaid said. "And it is absolutely essential that we in the United States of America figure out how, in the long run, to lessen our dependency on foreign energy."

He reiterated comments made in September that the U.S. needs to do a better job of coordinating economic, political and diplomatic means so the conflict can move from a military to a political issue.

"I would characterize what we're doing now as 80 percent military, 20 percent diplomatic, economic, political, educational, informational, intelligence, etc.," Abizaid said. "You've got to take that equation and change it. Make it 80 percent those other things."

Abizaid, who has dubbed the current conflict "The Long War," told The Associated Press in September it will take three to five years before Iraq's government is stable enough to operate on its own.

Despite the strain on the armed forces, Abizaid said Wednesday it is important to maintain a professional military without re-establishing a draft.