The former head of the U.S. central bank says in a new memoir that he believes the Iraq war is largely about oil.

Former Federal Reserve Chairman Alan Greenspan writes in his memoir to be released on Monday that he is "saddened that it is politically inconvenient to acknowledge what everyone knows - the Iraq war is largely about oil."

Defense Secretary Robert Gates disagreed in a televised interivew on ABC's This Week Sunday, saying the war is really about stability in the Middle East and trying to prevent rogue regimes from developing weapons of mass destruction.

Greenspan headed the U.S. central bank from 1987 until 2006, serving under four presidents. He earned praise for policies that many said encouraged the American economic boom in the 1990s.

Some of the information for this report provided by AP and AFP.