UK premier Tony Blair has endorsed US President George Bush's assertion that coalition troops must stay in Iraq as long as necessary to defeat terrorism.
The UK premier was talking ahead of the UK-hosted G8 summit
Mr Blair told the Associated Press it was "vital" the US-led coalition remained until the country stabilised.
Defeating "insurgents and terrorists" there would lead to the destruction of terrorism across the globe, he said.
Mr Blair argued the 11 September 2001 atrocities in the US upset the balance, raising fears of nuclear terrorism.
On Tuesday Mr Bush told US citizens that Iraq was the "latest battlefield in the war against terrorism".
He said: "We will stay in Iraq as long as we are needed - and not a day longer."
Mr Blair, in a pre-G8 summit interview, said the Iraq situation was a "monumental battle that affects our own security".
"You've got every bad element in the whole of the Middle East in Iraq trying to stop that country get on its feet and become a democracy."
He said that 11 September 2001 changed his perspective on the world.
"I took the view that if these people ever got hold of nuclear, chemical or biological capability, they would probably use it."
Low approval ratings
Mr Bush's address to the American people came on the first anniversary of the handover of power to an Iraqi interim government.
He attempted to answer growing criticism of the US presence, as opinion polls indicated disapproval of his handling of the war in Iraq.
Mr Bush's approval ratings have fallen to their lowest point in his presidency.
"Is the sacrifice worth it? It is worth it and it is vital to the security of our country," he said.
"The American people do not falter under threat - and we will not allow our future to be determined by car bombers and assassins.
"The only way our enemies can succeed is if we forget the lessons of 11 September."
No new treaty
More than 1,000 people - mostly Iraqis - have been killed since the new Iraqi government was formed in April.
The US death toll has pushed past 1,700 since the conflict began in March 2003.
The number of British troops killed in Iraq since the start of military operations is 88.
In his AP interview Mr Blair was also asked about differences with the US over climate change - a central plank of the UK premier's aspirations for the G8 presidency.
He said: "Obviously there is a disagreement over the Kyoto treaty and you are not going to resolve that disagreement.
"I cannot negotiate a new climate change treaty at the G8, that would be absurd," he said. "But I think there is more common ground if people are prepared to find it."