Mr Bush warned of the terrorists' ever-changing tactics

Linking their actions with insurgents in Iraq and Afghanistan, he said they all wanted to "establish safe havens from which to attack free nations".

Mr Bush said the UK terror plot was a "reminder that terrorists are still plotting attacks to kill our people".

He made the comments in his weekly radio address to the American people.

'Worst attacks yet'

"The terrorists attempt to bring down airplanes full of innocent men, women, and children," Mr Bush said.

"They kill civilians and American servicemen in Iraq and Afghanistan, and they deliberately hide behind civilians in Lebanon. They are seeking to spread their totalitarian ideology."

Mr Bush said that the alleged terror plot, which UK intelligence services claim involved a plan to destroy US-bound passenger planes using liquid explosives smuggled in drinks bottles, was "further evidence that the terrorists we face are sophisticated, and constantly changing their tactics".

US officials say that if the plan had not been foiled, the subsequent attacks would have been the worst since those on Washington and New York on 11 September 2001.

Since the 2001 attacks, Mr Bush has said that the US is engaged in a global war on terror.

He says that as well as intelligence efforts to foil terror plots against US civilians, the ongoing military campaigns in Afghanistan and Iraq are part of that same battle, as is Israel's conflict with Lebanon.