President Bush retreated yesterday from earlier claims, made by the White House and US military commanders, that Iran’s government had authorised the supply of weapons to Shia militants in Iraq.

He said it was well-known that components of deadly improvised bombs, which have been responsible for killing at least 170 American soldiers, had been provided by al-Quds force, an Iranian paramilitary organisation.

“What we don’t know is whether or not the head leaders of Iran ordered the Quds Force to do what they did. Either they knew or didn’t know. What matters is that [the weapons] are there,” Mr Bush told a White House press conference. His comments directly contradict a briefing by senior US military officers in Baghdad on Sunday who said that al-Quds had been operating on instructions “coming from the highest level of the Iranian Government”. Tony Snow, the White House press secretary, had explicitly endorsed the claim on Monday before appearing to backtrack when General Peter Pace, the chairman of the Joints Chiefs of Staff, cast doubt on its veracity.

Yesterday Mr Bush reacted sharply to questions implying that his Administration was tampering with intelligence material to justify a military strike against Iran. “The idea that somehow we’re manufacturing the idea that the Iranians are providing IEDs [improvised explosive devices] is preposterous,” said the president, who emphasised that the claims were “not a pretext for war”.

He said: “My job is to protect our troops. And when we find devices in that country that are hurting our troops, we’re going to do something about it, pure and simple.”

In his press conference yesterday and in interviews earlier this week Mr Bush has adopted a markedly less belligerent tone towards Iran than that used by his Adminsitration in the past two months. He said the biggest problem was “the Iranians’ desire to have a nuclear weapon”, and emphasised: “We have no desire to harm the Iranian people.”

Buoyed by this week’s diplomatic breakthrough in talks designed to eliminate North Korea’s nuclear programme, Mr Bush said real progress was being made towards a diplomatic solution on Iran.

“Like the Iranian issue, I wanted to solve the North Korean issue peacefully and the president has an obligation to try all diplomatic means necessary to do so. I’ve changed the dynamic on the North Korean issue by convincing other people to be at the table with us,” said Mr Bush, pointing to the influence of China, Japan and Russia is the six-party talks.

Mr Bush spent much of his press conference yesterday retrenching his position in Iraq as he effectively conceded in a Congressional resolution tomorrow that will formally express disapproval of his plans for a troop increase. But he used conciliatory language towards his opponents, saying: “I think you can be against my decision and support the troops, absolutely. But the proof will be whether or not you give them the money necessary to do the mission.”

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