“Operation Swarmer” came as Iraq’s deeply divided political leadership met again hoping to break a deadlock on forming a unity government that might avert sectarian civil war.

Signs of movement to end the paralysis did emerge, however, as US and Iranian officials said they could set aside years of hostility to discuss stabilising Iraq, where Teheran has gained influence with ties to fellow Shias in power.

US military officials on Thursday said the operation, involving 50 helicopters, was the biggest “air assault” since a similar airlift across Iraq just after the war in late April 2003. That operation was also by the 101st airborne division.

Military spokesman Lieutenant-Colonel Barry Johnson said that US-led forces are searching a 16-km by 16-km area for guerrillas and that no casualties have been reported by American or Iraqi forces.

The operation, which comes just ahead of the third anniversary of the US-led invasion which toppled Saddam Hussein, appears to be the latest US effort to show that Iraqi troops are improving their performance against insurgents.

A US troop withdrawal hinges on whether Iraqi troops can improve their skills after watching rebels armed with extensive intelligence and bombs kill hundreds of their comrades.

The US ambassador to Iraq, Zalmay Khalilzad, has been mediating tirelessly hoping that Iraqi leaders will finally bury their sharp differences and form a government three months after parliamentary polls.

Washington is also concerned that interference from regional Shia power Iran, which has close ties to the Shia-led Baghdad government, could further destabilise Iraq, a major oil producer.

US Secretary of State Condoleezza Rice told a news conference on a trip to Australia yesterday that she believed talks with Iran on stabilising Iraq would be “useful”.

The US embassy in Baghdad in a statement again accused Iran of meddling in its neighbour’s internal affairs, saying the Islamic Republic was carrying out “unhelpful activities” there.

The statement was issued one day after Iran said it accepted a proposal by leading Iraqi Shia leader Abdul Aziz Al Hakim to open a dialogue with the United States on Iraq. Fresh violence reminded all parties of the enormous challenges that lay ahead nearly three years since Saddam Hussein was toppled and Iraqis were promised a bright future.