More than 250,000 US troops are getting ready to take part in a war with Iraq, along with thousands of UK troops too.
Experts say there is almost no chance of Saddam Hussein leaving the country.
Other countries aren't happy with this latest move by the US, because they think that any military action should only happen if the United Nations agree.
No UN backing for war
On Monday a resolution that would have given UN permission for a war was withdrawn because some countries said they would never vote for it.
Other key Iraq developments:
The US advises all non Iraqi people, including journalists and weapons inspectors to leave the country
In the UK, cabinet minister and former foreign secretary Robin Cook resigns from the government in protest against war
On Tuesday the UK parliament will talk and then vote on whether British soldiers should join in with the war
Health Minister Lord Hunt resigns in protest against the war
Australia promises to send troops to help the fight against Iraq