A staged withdrawal of all 7,500 British troops now in southern Iraq could come by the end of next year, defence sources said.

Military commanders have made no secret of their wish to get out of Iraq, with senior sources critical of the decision to maintain such a large garrison.

Tony Blair is expected to urge America to open talks with Iran, Syria and other regional powers when he speaks to the Iraq Study Group, co-chaired by James Baker, the former US secretary of state, by video link on Tuesday.

President George W Bush is preparing to adopt a new strategy in Iraq after replacing Donald Rumsfeld as defence secretary with Robert Gates, a former member of Baker’s group.

Gates supports a dialogue with Iran and is understood to back the setting of political and military “benchmarks” that would enable American forces to be withdrawn to their bases and ultimately out of Iraq.

Senior sources have been suggesting for some time that the reason British troops remained in such numbers was that Blair was reluctant to embarrass Bush with any withdrawals before last week’s elections.

There is little doubt that given the option, British troops would have been pulled out earlier. Britain’s agreement to lead the Nato deployment in Afghanistan was based on an assumption its troops would have been largely withdrawn by the start of this year.

The British are preparing to hand back Basra by next March, allowing a cut in forces to just over 3,000. oDefence chiefs are so short of frontline troops they are planning to force all Territorial Army (TA) soldiers to serve at least one year out of five on operations, say senior defence sources. The plan is likely to cause anger within the TA, where only about a third of those eligible have been prepared to serve on operations abroad.

However, under a reorganisation in both the regular and territorial armies, defence chiefs are determined every possible resource is used.

The role of the TA — now to be called the Reserves — has changed from “home guard service”, said one senior officer. It is now regarded as a back-up force for frontline troops.

The reorganisation, the army’s second in as many years, follows two reviews that revealed there too few infantry units to sustain future deployments.

About 12,000 members of the TA have served in either Iraq or Afghanistan, but now commanders want the remaining 20,000 to be ready to deploy.

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