NATO and Afghan officials on Tuesday urged Taliban militants holding a southern town to lay down their arms and warned civilians there to "keep your heads down" as U.S. and Afghan troops prepare their first major offensive of the U.S. troop surge.

NATO's civilian chief in Afghanistan, former British Ambassador Mark Sedwill, said authorities were prepared to deal with an influx of refugees who may flee fighting in Marjah, the biggest town in the south under Taliban control.

Sedwill said civilian officials were prepared to follow up a military attack with programs to improve public services and restore Afghan government control.

"The success of the operation will not be in the military phase," he told reporters in a briefing at NATO headquarters in Kabul.

"It will be over the next weeks and months as the people ... feel the benefits of better governance, of economic opportunities and of operating under the legitimate authorities of Afghanistan," he said.

International officials believe the insurgency has been able to capitalize on widespread public anger over President Hamid Karzai's corruption-ridden government and failure to provide services after more than eight years of war.

Without giving a date for the attack, U.S. commanders and their NATO and Afghan allies have heavily publicized their plans to clear Marjah, an opium producing center southwest of the Helmand provincial capital of Lahkar Gah.

NATO commanders also have stressed that good governance and projects to improve services must also happen quickly to let Marjah's estimated 80,000 residents know that the government was ready to replace Taliban overlords and drug traffickers.

The governor of Helmand province said it was unusual but necessary to broadcast the plans for the offensive "to make the people aware that we are coming, that the purpose of this is to work for them, not just to conduct a military operation."

The advance notice has caused hundreds of farmers and other civilians to flee the area.

Gov. Gulab Mangal said a commission has been formed to handle the flow of refugees and any other fallout from the military action.

Mangal said at least 164 families had left the Taliban-influenced area. Afghan families have an average of six members, according to private relief groups.

"The commission is fully prepared. We have got tents. We've got food. We've got everything in place," he said at the joint press conference with Sedwill, declining to give specific numbers.

Authorities have not advised people to leave the Marjah area but have warned them to stay inside and avoid road travel once the operation begins.

Sedwill said the main question was whether Taliban militants in the area could be persuaded to join a government-promoted reintegration process.

"The message to them is accept it," he said. "The message to the people of the area is of course keep your heads down, stay inside when the operation is going ahead."

Mangal also said the government had received preliminary indications that some local Taliban were ready to renounce Al Qaeda and join the government's reintegration process.

"I'm confident that there are a number of Taliban members who will reconcile with us and who will be under the sovereignty of the Afghan government," he said.