The United States has spied on Iraqi Prime Minister Nouri Al-Maliki and other Iraqi leaders, according to US journalist Bob Woodward's fourth book on President George W Bush, The Washington Post reported.

"We know everything he says," one of Woodward's sources on the extensive spying operation is cited as saying in the book being released on Monday, the newspaper reported.

The book titled "The War Within: A Secret White House History 2006-2008," also says that the US troop surge of 2007 was not the primary factor behind the steep drop in violence in Iraq, the Post reported.

Woodward reports "groundbreaking" new covert techniques, beginning in 2007, enabled US military and intelligence officials to locate, target and kill insurgent leaders and key individuals in extremist groups such as Al-Qaeda in Iraq.

Woodward did not provide much detail about the covert operations and wrote he was asked to withhold specifics because of national security concerns, the newspaper said.

"The book portrays an administration riven by dissension, either unwilling or slow to confront the deterioration of its strategy in Iraq during the summer and early fall of 2006," The Post said.

The newspaper said Woodward also wrote about ongoing tension within the Bush administration over the quality and credibility of information about the progress of the war in Iraq.

US Secretary of State Condoleezza Rice complained about  the Defense Department "overconfident" briefings during the tenure of then Pentagon chief Donald Rumsfeld.

Rice is quoted as saying that Bush would get "a fable, a story . . . that skirted the real problems," according to the Post.

The book also depicts the development of a close working relationship between Bush and Maliki, the report said. Woodward writes that the surveillance of the Iraqi prime minister caused some consternation among several senior US officials who questioned whether it was worth the risk given Bush's effort to earn his trust, the Post reported.

Woodward is well known for his investigative work with fellow reporter Carl Bernstein that played a key role in forcing President Richard Nixon to resign in 1974 in the Watergate scandal.

Excerpts of the 487-page book will appear in The Post, where Woodward is an associate editor, on September 7.

Woodward's third book on the Bush presidency, "State of Denial," was a bestseller and put the White House on the offensive after he wrote that Bush resisted demands to boost US troops in Iraq and was misleading Americans about the level of violence there.

That book was tougher than the first two books he had written about the Bush White House since the Sept. 11 attacks, which were criticized by some as painting Bush as a hero. - Reuters