Admitting that the Iraq war has been difficult and longer than it was anticipated, United States President George W Bush [Images] has said that failure in the war-torn country will send a message to the friends of the US that 'you can't count on America'.

"Failure in Iraq would send a message to our friends that you can't count on America," Bush said on Thursday at a joint press conference with visiting British Prime Minister Gordon Brown.

"Success in Iraq will be a significant blow to both Al Qaeda [Images] and Iran's ambitions," he said.

During the talks, the two leaders discussed a wide range of issues including political, economic and environmental.

"I'm interested in succeeding in Iraq. This is a mission that is succeeding on the security front. It's getting better on the economic front. It's improving on the political front. We'll have the troops there necessary to succeed," Bush said.

He, however, admitted, "It hasn't been easy. It's been difficult. It's taken longer than I anticipated".

"A failure in Iraq would embolden Al Qaeda, would give them a huge victory, enable them to more likely establish a safe haven in a wealthy country to launch attacks against us," Bush said.

"A failure in Iraq would send a message to Iran that the US and its allies were not intent upon making sure that they stay within the borders of their country and they wouldn't take us seriously when it came to stopping their desires to have a nuclear weapon," he said.

"General Petraeus thinks we can win with fewer troops. That's why I accepted the recommendation. General Petraeus and Ryan Crocker (US ambassador to Iraq) know that the troops were necessary to provide stability for the political progress to be made that's being made and for the economy to improve," Bush said.

The President termed as 'false' speculation that his relationship with Brown is less special than that of former prime minister Tony Blair [Images].

"False. We've got a great relationship. Our special relationship has been forged in common values and history. We're making history together. We're dealing with a lot of problems. The most severe problem, as far as I'm concerned, is the willingness of people to murder innocent people to achieve their political objectives. This is the fundamental threat facing civilisation in the 21st century," he said.

"Prime Minister Brown sees the threat. He had to live through the threat. So our relationship is very special. I'm confident future presidents will keep it that way. There's just such a uniqueness in the relationship. That's not to say you can't have other friends, and we do," Bush said, adding, " But this is a unique relationship".

For his part, Brown maintained that this indeed is a 'special relationship', not just of governments but peoples.

"I look forward to its enhancement at all levels in the years to come. And I will work as hard as President Bush to make that relationship as strong and as enduring for the future," the British premier said.