US Secretary of State Colin Powell denied as "silly" a report that he learned of the decision to invade Iraq after Saudi Arabia was informed, as journalist Mr Bob Woodward has said.
Despite questions raised by a new book called Plan of Attackby Mr Woodward that Mr Powell had misgivings over the invasion, Mr Powell also said he knew he would support a war if he failed to find a diplomatic solution at the United Nations.
The book has fueled election-year claims of rifts in the administration and that President George W. Bush was eager to invade Iraq despite warnings over the dangers of an occupation.
Mr Powell, who has been perceived as the most reluctant among President Bush's key advisers to occupy Iraq, sought to defend his positions on the war after Mr Woodward said he tussled with other top officials and was out of the loop on the final decision.
"When I told the president, 'This is going to be difficult, especially in the aftermath, and we are responsible for Iraq,' then I was doing my job," Mr Powell said.
President Bush told national security adviser Ms Condoleezza Rice, vice president Mr Dick Cheney and defence secretary Mr Donald Rumsfeld first about his decision to go to war in January 2003, according to Mr Woodward.
A detailed plan was also shown to Saudi Ambassador to the United States Prince Bandar bin Sultan before President Bush told Mr Powell of his final decision, Mr Woodward said.
"That's silly because I participated in the development of the plan. I commented on the plan when it was being developed, and I knew when Vice President Cheney and Mr Rumsfeld and General [Richard] Myers were going to go brief Prince Bandar on a plan, a plan that I was intimately familiar with," Powell said.