The US Congress today began a three day debate on authorising President George W Bush to use force to oust Iraq's Saddam Hussein.
If forced into war, "we will prevail," the president said. "I want to thank members of both political parties for realising the seriousness of this issue," Mr Bush said as debate opened in the House.
"At this moment, the people's house begins debate on one of the most difficult questions we will ever face," said Mr David Dreier, a California Republican.
Both the House and Senate hope to conclude by Thursday night, with expectations they would approve a resolution providing the president wide latitude to take military action to topple Saddam.
Anticipating an overwhelming vote of support in Congress, Mr Bush told a Tennessee rally today: "Military option is my last choice, the last choice.
"But should we commit our military, we'll be ready. We'll be prepared. We'll have a great plan and make no mistake about it, we will prevail."
Mr Bush said that Saddam was "a homicidal dictator who is addicted to weapons of mass destruction," and that if he succeeds in obtaining nuclear weapons to add to his biological and chemical stockpiles, he "would be in a position to blackmail anyone who opposes his aggression."
In Baghdad, the Iraqi government described Mr Bush's speech as an attempt to justify an attack.
"The speech contained misleading information through which Bush is trying to justify an illogical and illegitimate attack on Iraq," said Foreign Minister Mr Naji Sabri Sabri.
The British Foreign Minister Mr Jack Straw said at the start of a Middle East tour today that war with Iraq was not inevitable but Baghdad must disarm or face the consequences.
"The use of force in Iraq is not inevitable. President Bush made that crystal clear in his speech yesterday, which I greatly welcome, where he set out effectively that there was a clear choice for Saddam Hussein," Mr Straw told reporters in Egypt.