The activities of al-Qaeda in two of Iraq’s most troubled cities could keep US combat troops engaged beyond the June 30 deadline for their withdrawal, the top US commander in the country has warned.

US troop numbers in Mosul and Baqubah, in the north of the country, could rise rather than fall over the next year if necessary, General Ray Odierno told The Times in his first interview with a British newspaper since taking over from General David Petraeus in September.

He said that a joint assessment would be conducted with the Iraqi authorities in the coming weeks before a decision is made.

Combat troops are due to leave all Iraqi cities by the end of June. Any delay would be a potential setback for President Obama, who has pledged to withdraw all combat forces from Iraq by August 2010 as he switches his focus to Afghanistan.

The ultimate decision on keeping or withdrawing troops would be taken by Nouri al-Maliki, the Iraqi Prime Minister, handing him a big dilemma, given the desire by most Iraqis for the US military to leave the country.

Tens of thousands of supporters of Moqtada al-Sadr, the antiAmerican Shia cleric, marched through Baghdad yesterday, the sixth anniversary of the fall of the capital, to demand the withdrawal of US forces.

General Odierno, 54, said that he was also concerned about the risk of renewed conflict between Arabs and Kurds in northern Iraq, where tensions are rising over the ownership of territory. He also cited the “very dangerous” threat posed by Iranian-funded militants, who appear to be styling themselves on Lebanon’s Hezbollah.

General Odierno, a bald, imposing 6ft 5in, was speaking as he sat outside the back of the Saddam-era mansion that he calls home, next to a man-made lake on a military base in Baghdad. Touching on a range of issues, he said that he was not worried by a recent spate of deadly bombings against Shia targets blamed on al-Qaeda. He said they were designed to coincide with key dates such as the anniversary of Baghdad’s fall and rejected the idea that they signalled a fresh round of sectarian war.

The general has long experience of Iraq: he arrived in April 2003, after the invasion, and led the US division that was ultimately responsible for capturing Saddam Hussein; he was No 2 to General Petraeus in 2007; and is now on his third tour in charge of the American withdrawal.

Under an agreement between Washington and Baghdad, all 140,000 US troops must be out by the end of 2011.

Despite the rise in the number of attacks, overall violence is still far below levels of two years ago when the surge of an extra 30,000 US forces – a strategy created and implemented by General Odierno and his boss, General Petraeus – was just getting started. That risk paid off, subduing a civil war that was killing thousands of Iraqi civilians and scores of American soldiers every month.

General Odierno said that his darkest days in Iraq were when he was in charge of day-to-day combat operations in 2007. During that 15-month tour he signed hundreds of letters of condolence to the parents of service-men and women from the US, Britain and other coalition countries. “I always felt [the surge] would [succeed] but those were the times when you were wondering whether this will work or not,” he said.

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