HMS Ark Royal, an aircraft carrier, and the helicopter carrier, HMS Ocean, are already on their way to the Gulf.
Time running out
Britain and America think the Iraqi leader, Saddam Hussein, has got secret weapons of war hidden in Iraq, which he could use against them if he's not stopped.
But Britain's defence boss, Geoff Hoon, said the troops going out did not necessarily mean there would be a war.
However, the British Foreign Secretary, Jack Straw, said that time was running out for Saddam. He said he must agree to what the UK and the US wanted, or face the possibility of war.