President Bush today marked the fifth anniversary of the start of the Iraq war with the message: "The world is better, and the US is safer."

In a bullish speech at the Pentagon, in which he repeatedly linked the conflict in Iraq with the worldwide war against Islamist terror, Mr Bush said any rapid drawing down of troops would risk emboldened terrorists launching a "repeat" of the September 11 attacks.

He also claimed that the surge into Iraq, launched last year, had been a success in reducing attacks against US troops, restoring order, and opening the door to "a major strategic victory in the broader war" on extremism.

Yet the President's optimism over the invasion was in stark contrast to many in America today, with one leading newspaper marking the anniversary by publishing a critical editorial over the way the invasion was carried out and with demonstrators clashing with police across the road from the Pentagon.

Speaking to an audience of military chiefs, Mr Bush admitted that the invasion had come at a cost, with 3,988 casualties of US troops since the war began. He conceded that it was "understandable" that people wanted to debate "whether the fight is worth winning". But he added: “The answers are clear to me: Removing Saddam Hussein from power was the right decision, and this is a fight America can and must win."

In further reference to critics of the war, he said: "No one would argue that this war has not come at a high cost in lives and treasure, but those costs are necessary when we consider the cost of a strategic victory for our enemies in Iraq.

"If we were to allow our enemies to prevail in Iraq, the violence that is now declining would accelerate – and Iraq could descend into chaos. Al-Qaida would regain its lost sanctuaries and establish new ones – fomenting violence and terror that could spread beyond Iraq's borders, with serious consequences to the world economy."

In another reference to the wider battle against worldwide terror, Mr Bush said any substantial withdrawal would be viewed by enemies of the US as a retreat, leading to a possible repeat of the September 11, 2001, attacks.

"Enemies would see an American failure in Iraq as evidence of weakness and a lack of resolve," he said. "To allow this to happen would be to ignore the lessons of September 11, and make it more likely that America would see a repeat of the attack."

Claiming the surge, which saw an influx of US troops into Iraq last year, had been a success in reducing attacks, he added that the overall war against terror had benefitted. "The surge has done more than turn the situation in Iraq around – it has opened the door to a major strategic victory in the broader war on terror," he said.

The president was given a round of applause during what was labelled his most upbeat assessment of Iraq since his 'mission completed' speech in May 2003, when he said: "Because we acted, the world is better and the US is safer."

However the Democratic presidential candidates, marking the anniversary with speeches on their plans for the country, offered a very different appraisal.

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