A longtime liberal Democrat, Senator Edward Kennedy said Bush and his advisers capitalised on the fear from the September 11 attacks and put "a spin on the truth to justify a war that could well become one of the worst blunders in American foreign policy."
Kennedy, who served in the US Senate since 1962, said Bush timed the Iraq debate to divide Democrats and help Republicans win 2002 congressional elections by distracting attention "from the troubled economy and the troubled effort to capture Usama bin Ladin."
Speaking at the Centre for American Progress, Kennedy said Bush should not have sent US troops "in harm's way in Iraq for ideological reasons and on a timetable based on the marketing of a political product."
He said the president "has broken faith with the American people, aided and abetted by a congressional majority willing to pursue ideology at any price, even the price of distorting the truth."
Kennedy's criticism is significant, particularly since it comes barely days after former Treasury Secretary Paul O'Neill accused Bush of plotting the Iraq war from the very start of his presidency.
The Democratic lawmaker was bitter about the possible consequences of the war, saying that the military adventure was a setback to the effort to stop "terrorism".