US officials said on Monday that American troop levels in Iraq were likely to remain well above 140,000 for the next few months, although they would not confirm reports that the 3,500-strong First Armoured Division had been ordered to remain in Iraq beyond its official tour of duty.

Growing sectarian conflict between Iraqi militias in the last few months and the continuation of the mostly Sunni insurgency against US forces has complicated the Bush administration’s goal of “standing down as the Iraqis stand up”. The overall US troop presence in Iraq has risen from 127,000 in July to 142,000 this week.