However, addressing a joint session of the Commons Defence and Foreign Affairs committees, he gave no promises of substantial reductions and said that decisions on any reduction of troops would have to wait until security conditions in southern Iraq, where the British are based, had stabilised.

He told the MPs he was “aware of the possibility” that any future American strike on militia in Sadr City, the Shia slum in Baghdad, might have repercussions in the Shia community in Basra. He said that contingency plans existed for that eventuality.

However, he and Margaret Beckett, the Foreign Secretary, jointly questioned by the MPs, both emphasised that southern Iraq was different from Baghdad in terms of the level of violence, and there was still hope that a reduction in forces could happen this year.

Defence sources said that under present military planning, the next rotation of troops in Basra — with 1 Mechanised Brigade taking over from 19 Light Brigade in the early summer — was due to go ahead without any cut in numbers, maintaining the strength of the British presence at about 7,000.

“If the security conditions are looking better by then it might be possible to remove the odd unit from the brigade, but not a substantial amount,” one defence source said.

Mr Browne told the MPs that the situation had not changed since November when he had said that he had every expectation that he would be able to announce a withdrawal of troops in 2007 and that he hoped it would be “in the thousands”. He said that Tony Blair had made it clear he would make a statement to the Commons next month or in March about the security situation in Basra once Operation Sinbad, the drive to clear extremists from Basra city, was over.

Mr Browne told the MPs that as an indication of the success of British efforts in the south, the number of murders being committed in Basra had gone down from 139 in June last year to 29 in December.

Both Mr Browne and Mrs Beckett emphasised that the present strategy in Basra and elsewhere in southern Iraq would continue as before.

Air Chief Marshal Sir Jock Stirrup, the Chief of the Defence Staff, sitting alongside the two ministers, reassured the MPs that the US had made no request for British troops to serve elsewhere in Iraq.

He also said that plans to put all British troops in Basra into one base, at the airport site, were going ahead and should be completed soon. There are also troops at Shaibah, a logistics base, south of Basra.

Mrs Beckett told the MPs that the Government intended to carry on talking to Iran and Syria and that it supported the Iraq Study Group recommendation that America should include Iran and Syria in discussions about Iraq’s future. Mr Bush made it clear in his speech that he has rejected this proposal.

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