US-led forces on Friday pressed on with an offensive against suspected guerrilla targets near the northern Iraqi town of Samarra in their latest bid to weaken a raging insurgency, witnesses said.

"Operation Swarmer" came as Iraq's deeply divided political leadership prepares to meet again hoping to break a deadlock on forming a unity government that might avert civil war.

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.

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

He said 50 people have been detained and 30 remain in custody. The US military usually describes insurgents as "terrorists" so Iraqis netted in the raids could have just been ordinary farmers from rural areas near Samarra.

The offensive comes at a time when the US ambassador to Iraq, Zalmay Khalilzad, has been mediating tirelessly to narrow differences among Iraqi politicians still struggling to form a government three months after parliamentary polls.

A leading Sunni Arab politician criticized the US assault, saying it would send a discouraging signal at a time when Iraqi leaders are seeking a political solution to the country's woes.

"This large operation that used airplanes is sending a signal to parliament and Iraqis that the solution is military and not political," he said.

Iraqi Defence Ministry spokesman General Salih Sarhan criticized the attention being given to the assault, describing it as one of many operations aimed at rooting out rebels and seizing weapons.

"This operation is not an invasion and the media have overreacted. The operation aims to search and control the area and launch raids against some suspected places," he said.

The sound of what appeared to be heavy US machineguns crackled in the village of Jillaam near Samarra overnight as a fire raged and flares arched overhead, witnesses said. The chant of "God is Greatest" a guerrilla rallying cry cut through the sound of heavy gunfire.

But there was no sign of a counter attack by insurgents who have kept Iraq destabilised despite several American assaults in several parts of the country torn apart by sectarian tensions.

Iraqis, who watched their country slide towards civil war after the bombing of a Shi'ite shrine in Samarra last month unleashed a surge of sectarian violence, were sceptical over the offensive near the city 100 kilometres north of Baghdad.

"We often hear about these offensives, but frankly I really don't see what their purpose is," said Baghdad resident Alaa.

The assault was announced on Thursday after a first session of the new Iraqi parliament was reduced to an empty gesture by deadlock on forming a unity government seen as vital to avert civil war.

Signs of movement to end the paralysis did emerge, however, when US and Iranian officials said they could set aside years of hostility to discuss Iraq. And Iraqi political sources said a new alliance of parties may be formed in the hope of a breakthrough.

Urging the formation of a unity government, the US commander in the Middle East said the United States should be able to continue to cut its own troop levels if Iraqi forces show progress.

(China Daily 03/18/2006 page7)