At a ceremony at Central Command's headquarters at MacDill Air Force Base in Tampa, Florida, Defense Secretary Donald Rumsfeld took the Centcom flag from Franks and passed it to Abizaid, in a symbolic transfer of leadership.

"I know of no one more qualified to follow in Tom Franks's footsteps," Rumsfeld said.

Abizaid, 52, will oversee troops in a region that encompasses 25 countries in the Middle East and Southwest Asia, an area that spans some 3,100 miles (5,000 kilometers) east to west and 3,600 miles (5,750 kilometers) north to south.

It includes the world's largest oil reserves in Saudi Arabia and the Gulf and major trade routes through the Suez Canal and the Red Sea.

The United States has about 250,000 troops in the region, including 145,000 in Iraq, another 9,000 in Afghanistan and about 1,500 in the Horn of Africa, military spokesmen say.

Abizaid is an expert in Arabic affairs with a master's degree in Middle Eastern studies from Harvard University.

He assumes command at a time of dramatic changes in the region as a result of the US-led invasion of Iraq.

In addition to the occupation of Iraq, he will oversee a withdrawal of US forces from Saudi Arabia and a continuing struggle against al-Qaeda militants.

Abizaid, who is of Lebanese descent, studied at the University of Jordan in Amman and served as an operations officer with a UN Observer Group in Lebanon.

A West Point graduate, his 30-year military career has spanned US actions from Grenada to Kosovo.

Abizaid is married and has three grown children.

WAR.WIRE