BAGHDAD: The US has been forced back into combat in Iraq five months before the remaining 46,000 American troops were due to leave..

Instead of a calm countdown to December 31, when the US “trainers and assisters” can depart, leaving an Iraqi security force in charge, troops have found themselves under attack.

Washington’s combat operation was formally ended almost a year ago but in the past six weeks 18 US soldiers have been killed. As trainers, they are allowed to defend themselves, but the sudden rise in violence has forced the military, with the blessing of the Pentagon, to go on the offensive.

There is forensic evidence that Iran is behind the attacks. Despite denials from Tehran, sophisticated weaponry, including armour-piercing projectiles, have been smuggled from Iran to Shia militants in Iraq, who are being trained by Iranians to target US troops. It is the same game Tehran played during the height of the insurgency in Iraq after the US-led invasion in 2003. Then, Tehran’s plan was to inflict defeat on the US occupiers. They failed. This time Iran is arming its militants in Iraq to make sure that every US soldier leaves by December 31, never to return.

The reawakening of the insurgency has been timed to put maximum pressure on the government of Iraqi Prime Minister Nouri al-Maliki.

He has been in negotiations with the US in recent weeks over whether to ask them to retain a military presence after the deadline.

Leon Panetta, in Baghdad on his first foreign trip since becoming US Defence Secretary on July 1, voiced his concerns about the violence and called for a full-scale pursuit of the Iran-backed insurgents. He made it clear to Mr Maliki that he wanted the Iraqi military to take responsibility for counter-attacks, but that he expected US soldiers to play their part in thwarting Iran’s objectives.

Mr Panetta wants the Baghdad government to make up its mind soon about whether to seek an extension of the US military role. There are unofficial reports that a force of between 5000 and 10,000 is under consideration to help with training in areas such as air defence, aviation and intelligence integration.

If Iraq is to be confident about securing its borders against a hostile neighbour, these gaps in capability need to be filled, and Mr Maliki knows that he will have to turn to the US for help.

But Mr Maliki is facing a political conundrum: how to ask Washington to stay when a key figure crucial to the sustainability of his administration, Hojatoleslam Moqtada al-Sadr, is demanding that no US troops remain after the deadline. The radical anti-US Shia cleric has threatened to resume armed attacks against US troops if they stay. His al-Mahdi army, formed in 2003, was responsible for some of the deadliest attacks on US troops.

Mr Maliki also knows that Tehran is waiting for the decision, and the burst of attacks on US troops is a reminder of the troubles ahead if he asks the Americans to stay.

US President Barack Obama’s “final withdrawal” deadline was supposed to be the day when he could tell the American people the war in Iraq was finally over — not “mission accomplished” as his predecessor declared prematurely in May 2003, but an end to the large-scale US troop presence there.

If the US military is asked to stay, albeit in smaller numbers, the risk is that the troops remaining will become targets.