The US House of Representatives has voted to authorise President Bush to go to war against Iraq.
The Republican-led House had been debating the measure which allows the president to use force against Baghdad if the United Nations fails to disarm Iraq.
The Senate is expected to endorse the step on Friday.
The president and his supporters have spent several days lobbying Congress to support the resolution.
However, the resolution encourages Mr Bush to pursue all diplomatic means before he decides on any attack.
It also stipulates that he reports to Congress every 60 days if he does take action.
The move comes amid a growing row over whether or not the CIA genuinely believes that Saddam Hussein poses an immediate threat.
Before the vote, the BBC's correspondent in Washington, Justin Webb, said some Democrats had been planning to vote no.
They point to a recently declassified letter from the CIA director, George Tenet, to a Congressional committee in which he appeared to cast doubt on the immediacy of the threat from Saddam Hussein, saying the Iraqi leader seemed to be drawing a line short of mounting terrorist attacks on the United States.
Retaliation fear
The letter added that there was a risk of Saddam Hussein using weapons of mass destruction in response to an American strike.
One Democrat Congressman said President Bush was risking triggering the very thing he was trying to prevent — the use of these weapons.
Mr Bush and congressional leaders agreed on a draft resolution at a meeting last week.
The text authorises the president to use force against Iraq in a manner "necessary and appropriate" to protect US national security and enforce UN resolutions.
It calls on Mr Bush to certify to Congress — either before a military strike or very shortly afterwards — that diplomatic and other peaceful means have failed.
In a latest round of diplomacy, UK Prime Minister Tony Blair has arrived in Moscow to try to gain support for a new UN resolution compelling Iraq to disarm.
Russia has resisted US and UK calls for a new resolution which would include the threat of force against Iraq.
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