President Bush last night unveiled plans for a reduced, but enduring, US military presence in Iraq just hours after hopes of pacifying the country were dealt a devastating blow.

A roadside bomb killed Sheikh Abdul Sittar Bezea al-Rishawi, who led the grassroots Sunni uprising against al-Qaeda and helped the US military drive the terror organisation from great swaths of western Iraq.

The tribal leader, who inspired the Anbar Awakening, died yesterday along with two bodyguards as he returned to his heavily-fortified home outside Ramadi. His armoured vehicle was almost completely destroyed. His assassins — almost certainly al-Qaeda — followed it up with a car bomb.

Sheikh Sittar, 36, had been lauded earlier this week by General David Petraeus, the top US commander in Iraq, during testimony to Congress, for helping to transform a region which was once the heart of the anti-American insurgency into one of the safest provinces in Iraq.

As recently as 11 days ago he met Mr Bush, during a surprise presidential visit to Anbar where he was praised for rejecting “murder and violence in return for moderation and peace”.

His assassination, on the first day of Ramadan, cast a shadow over Mr Bush’s sombre prime time television address to the American people. Paying tribute to the “brave sheikh”, Mr Bush said Iraq was “fighting for its survival”. America’s moral and strategic interests were to defeat those who “threaten its future and also threaten ours”.

The President was speaking from the Oval Office after a week in which General Petraeus and Ryan Crocker, the US Ambassador to Iraq, had delivered to a sceptical Congress their report on the progress made since Mr Bush began his surge of additional troops earlier this year.

Acknowledging that many Americans wanted to withdraw from Iraq, he said: “The principle guiding my decisions on troop levels in Iraq is return on success. The more successful we are, the more American troops can return home.”

US military successes, said Mr Bush, “now allow us to begin bringing some of our troops home” in a redeployment which will cut the current US military strength in Iraq from 168,000 to about 135,000 by next summer.

But Mr Bush made clear that substantial numbers of troops would have to remain for years, eventually focusing on more limited tasks, such as training Iraqi forces. He talked of an “enduring relationship” with Iraq that will require US political, economic, and security engagement that extends beyond my presidency”. Gambling his remaining 18 months in office and his Iraq legacy on an appeal for people to “come together”, he said: “It is never too late to support our troops in a fight they can win.”

This attempt to bind his successor after the 2008 presidential elections into what many regard as a failed strategy has infuriated Congressional Democrats. Opponents say the Iraqi Government has failed to meet many of the benchmarks for progress set by Congress.

Mr Bush hinted at his own frustration, saying: “I have made it clear” the Baghdad Government must do better. He suggested the reconciliation achieved by Sheikh Sittar was helping to change national politics as well.

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