Global Policy Forum

By Sean Rayment and Philip Sherwell

America is preparing to pour thousands of extra troops into southern Iraq amid fears that Gordon Brown is committed to withdrawing British troops from the region early next year. The White House and the Pentagon are understood to have drawn up detailed plans to secure the vital "umbilical cord" link road between Baghdad and Kuwait when the British depart. Washington is also concerned that a British pull-out will leave the border with Iran undefended, as well as undermining US operations at a time when political pressure is mounting for an American withdrawal.

Tensions are understood to have deepened between London and Washington after Mr Brown's recent visit to the US, amid fears the Prime Minister is distancing himself from the Bush regime and its military objectives. Military chiefs in the US have been "dismayed" by the threat of a unilateral pull-out from southern Iraq by British forces.

The Sunday Telegraph has also learnt that neither the British nor the Americans have a "Plan B" for sending troops back into Iraq if the country descends into chaos when the coalition finally withdraws. One senior source said: "Whether or not we go back in if it all goes horribly wrong is the strategic question to which neither the US nor the British government has an answer. "It seems to be lost on the British and American governments that Iraq holds the world's second-largest oil reserves. There is also the nightmare scenario of Iraq becoming an Islamic fundamental state, willing to give succour to groups like al-Qaeda."

Whitehall sources admit that there is a firm consensus among British military chiefs that maintaining a presence in Iraq after the control of Basra passes to the Iraqis in November is "pointless". But while British generals firmly deny that they have been defeated in southern Iraq, there is also an increasing acceptance that the mission is facing "strategic failure" and that the war is a "lost cause". One senior officer, who has served on operations in Iraq, said: "In terms of intervention operations, the military can never deliver success if the policy is wrong - and in terms of Iraq the policy of intervention was wholly wrong from start to finish."

Gen David Petraeus, the American commander of coalition forces in Iraq, is understood to have held discussions with Lt Gen Graeme Lamb, who until recently was the British deputy commander in Iraq, and Lt Gen Bill Rollo, the present incumbent, over the intentions of the British force after it hands over Basra. Gen Petraeus will deliver an interim report next month to the Bush administration on the success of his 22,000-strong troop surge in Baghdad. Any suggestion that the plan is working will put pressure on Mr Brown to keep British forces in Iraq.

Ken Pollack, a foreign affairs expert at the Washington-based Brookings Institution, who returned last month from an eight-day visit to Iraq, dismissed last week the British presence in southern Iraq as "meaningless". He said: "I am assuming the British will no longer be [in southern Iraq]. They are not there now. We have a battle group holed up in Basra airport. I do not see what good that does except for flying people in and out. It's the wild, wild west. Basra is out of control." John Pike, the director of globalsecurity.org, an American defence think-tank, said the 300-mile stretch of Route Tampa that runs from Baghdad to Kuwait was a crucial lifeline for US military operations. "It's the umbilical cord that connects the war in Iraq to the rest of the world," he said. "It will have to be secured."

About 2,000 trucks a day travel down the highway in high-security convoys, carrying more than 90 per cent of the food, water, ammunition and equipment for the 161,000-strong US force. The route remains a key target for insurgents and just last week two British soldiers were killed on it while providing security for a convoy. Patrick Mercer, a former Army commander and Tory MP, added: "Whatever withdrawal timescale we adopt, we have got to understand that our commitment to Iraq is not over. We've got to face the prospect that the situation in Iraq could get worse. The question is what are our plans and responsibilities to a county whose problems we have contributed to rather than solved."