Our war-weary Iraq troops could soon be fighting the Taliban in Afghanistan

Army insiders fear expanding the size of Britain's force fighting the Taliban will cancel out the benefits to the overstretched Army of quitting Basra.

Senior commanders believe the 7,100 troops in Afghanistan will need to be dramatically increased if they are to have a chance of driving out the Taliban, sources have told the Daily Mail.

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The mission of controlling Helmand Province, where most British forces are fighting, is increasingly seen as a divisional task, requiring nine battlegroups of around a thousand fighting men each.

But at present the UK only has three battlegroups available and, despite repeated appeals to Nato allies, there is no sign of other countries providing the scale of support required.

British commanders have admitted privately that although their men beat the Taliban time and time again they lack the numbers needed to occupy the ground they win, allowing the enemy to slip back into "cleared" areas.

The Ministry-of Defence said last night it had "no plans" to increase British forces in Afghanistan beyond the published goal of 7,800 by the end of this year.

But senior sources admitted proposals were being considered for a dramatic expansion of the UK mission. Ministers can expect to face intense political pressure in trying to justify such a step.

In Iraq, meanwhile, Britain has 5,500 troops remaining but nearly all of these could be withdrawn before the end of next year.

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The pull-out is already becoming bitterly controversial, with leading U.S. defence figures claiming UK forces have lost and insurgent leaders accusing them of 'giving up' and being forced out.

An Army source said the Germans, French and Italians were all unable to supply any more troops to Afghanistan.

The source added: "The West's dirty little secret is that we don't have enough infantry to hold the ground. It's now very likely that the numbers freed up from Iraq will be soaked up in Afghanistan.

"The question is: Have we got the will to do it, for years on end? Has Nato got the will?"

Britains' ambassador to Afghanistan, Sir Sherard Cowper-Coles, has warned that helping stabilise the country could take 30 years.

Meanwhile, a poll of American foreign policy experts shows most believe President Bush's military "surge" in Iraq has failed, and U.S. troops should be withdrawn within 18 months.

Nine out of ten say the world is more dangerous now than before Iraq was invaded.

The poll of senior figures including two former secretaries of state, intelligence officers and military leaders came as Pentagon chiefs revealed that the U.S. Army is running out of combat soldiers.

Army chief of staff, General George Casey, said: "The demand for our forces exceeds the sustainable supply."

Presidential hopeful Hillary Clinton called for the U.S. to start bringing troops home, even though she said the latest tactics in Iraq were paying off.