BAGHDAD (REUTERS) - Iraq's Prime Minister urged people in the besieged city of Falluja on Monday to drive out Al-Qaeda-linked insurgents to preempt a military offensive that officials said could be launched within days.

In a statement on state television, Mr Nuri al-Maliki, a Shi'ite Muslim whose government has little support in Sunni-dominated Falluja, said tribal leaders should help expel the militants, who last week seized key towns in the desert leading to the Syrian border.

"The Prime Minister appeals to the tribes and people of Falluja to expel the terrorists from the city in order to spare themselves the risk of armed clashes," read the statement.

A provincial official said security forces had regained control of another town, Ramadi, forcing militants to the east where they were holding out in mosques and homes. Air raids would flush them out, he told Reuters.

"The air force will end this battle in the next few hours,"said Mr Falih al-Essawi, a member of the council running Anbar province, adding that government workers and students in Ramadi had been told to return to work and school on Tuesday.

Two local tribal leaders in Falluja said meetings were being held with clerics and community leaders to find a way to persuade fighters from the Islamic State of Iraq and the Levant (Isil) to leave Falluja and avert further violence.

Iraqi forces have shelled and launched multiple airstrikes against militants over the past week, whilst armed Sunni tribesmen from the area are fighting on both sides. Officials say dozens of militants have been killed, but the number of casualties among civilians, security forces and tribal fighters is not yet clear.

Mr Maliki ordered the army, which is currently surrounding Falluja, not to attack residential areas as his forces prepare an offensive that has echoes of US assaults in 2004 on the city, some 40km west of Baghdad's main airport.

Security officials said Mr Maliki, who is also commander in chief of the armed forces, had agreed to hold off an assault for now at least to give tribal leaders in Falluja more time to drive out the Sunni Islamist militants on their own.

"No specific deadline was determined, but it will not be open-ended," a special forces officer said of plans to attack.

"We are not prepared to wait too long. We're talking about a matter of days only. More time means more strength for terrorists".

Isil has emerged in Syria's civil war as an affiliate of the international Al-Qaeda network and a powerful force among Sunni Muslim rebels seeking to oust President Bashar al-Assad.

In Iraq, it has been tightening its grip on Anbar province, a thinly populated region the size of Greece, with the stated aim of creating a Sunni state straddling the border into Syria's rebel-held eastern desert provinces.

But last week's capture of positions in Ramadi and large parts of Falluja was the first time in years that Sunni insurgents had taken ground in the province's main towns strung along the Euphrates river, and held their positions for days.

The White House said on Monday it would speed up deliveries of equipment to help Iraq battle the militants, including additional shipments of Hellfire missiles as early as this spring, 10 ScanEagle surveillance unmanned aerial vehicles (UAV) in coming weeks and 48 Raven surveillance UAVs later this year.

The United States (US) said on Sunday it would help Mr Maliki fight Al-Qaeda, but would not send troops to Iraq. An Iranian official offered similar help.

"CITY OF MOSQUES"

When Iraqi police broke up a Sunni protest last week in Ramadi, the capital of Anbar, deadly clashes fanned tensions across the province that was the heart of the insurgency after the 2003 US invasion that brought Shi'ite majority rule.

The tribes of Anbar helped turn the tide of that insurgency at its height in 2006, banding together and making common cause with US troops to rout Al-Qaeda.

The group's resurgence has divided people in Anbar, where many accuse Mr Maliki of shutting Sunnis out of power and being a pawn of Shi'ite Iran. Some sympathise with and support the Islamist militants, or are too fearful to move against them.

Others have vowed to help the government regain control.

"We are going to have an important meeting this evening and that will include some Al-Qaeda fighters in Falluja to convince them to leave the city and deprive Mr Maliki of a pretext to push his army inside the city," said one tribal leader.

"We should make Al-Qaeda fighters understand that their staying in Falluja will create rivers of blood."

Known as the "City of Mosques" and a focus for Sunni faith and identity in Iraq, Falluja is home to some 300,000 people and was badly damaged in two offensives by US forces against insurgents in 2004.

In recent days, residents have been fleeing the town in droves to escape fighting as well as shortages of food, drinking water, and frequent power cuts.

"The situation in Falluja is getting worse. There are gunmen everywhere," said doctor Mohammed al-Nuaimi, a resident of the city who spoke to Reuters via telephone as he packed his belongings and prepared to leave.

"We can't tell who's a friend and who's an enemy. I lost my elder brother in 2005 - he was killed by the Americans - and now I see same scenario happening. I'm not ready to feel the pain again."

The militants have also received help in Falluja from disgruntled tribesmen who have joined forces with them.

Much of Iraq's US-equipped army is drawn from the Shi'ite majority and faces recalcitrance if not outright hostility in Anbar, which covers about a third of the country's territory.

Across the border, Al-Qaeda fighters have also captured swathes of Syria and are battling with fellow Islamist brigades as well as government forces.

Two years after US troops ended a near-decade long occupation, violence in Iraq underlines how civil war between Syrian rebels backed by Saudi Arabia and other Sunni powers on one side and Assad, an ally of Shi'ite Iran, on the other has inflamed a broader confrontation along sectarian lines.