The revelation casts doubt on the public insistence by US and British officials throughout 2002 that no decision had been taken to go to war, pending negotiations at the United Nations.

Rumsfeld's War is by Rowan Scarborough, the Pentagon correspondent for the conservative Washington Times newspaper, which is known for its contacts in the defence department's civilian leadership.

"On February 16 2002, Bush signed a secret national security council directive establishing the goals and objectives for going to war with Iraq, according to classified documents I obtained," Mr Scarborough wrote, in an account of the "global war on terrorism" as seen from the office of Donald Rumsfeld, the defence secretary.

The next month, he writes, the head of central command, General Tommy Franks, conducted a "major Iraq war exercise code-named "Prominent Hammer", and in April he briefed the joint chiefs of staff on the invasion plan.

"Franks's plan called for 200,000 to 250,000 troops and a two-front land war... striking from Kuwait and from Turkey," the book says.

The national security council refused to comment on the book's claims about the February directive. "I don't do book reviews," a White House official said.

Ivo Daalder, an official in Bill Clinton's national security council, said a national security presidential directive was "the most formal way that decisions by the president and others are communicated to the rest of the government."

Rumsfeld's War reproduces excerpts from a secret Defence Intelligence Agency briefing document in July 1999 about future threats to the US.

It portrays Saddam Hussein's Iraq as a threat only if sanctions were lifted. But the administration decided that neither inspections nor sanctions were working, partly as a result of later discredited reports that Saddam had stockpiled WMDs.

http://www.guardian.co.uk/usa/story/0,12271,1154577,00.html