MINGORA, Pakistan - The military offensive to expel the Taliban from Pakistan's Swat Valley could take another two months to complete, and troops may have to stay for a year to prevent militants from retaking control, commanders said Wednesday.

The armed forces have secured control over several key towns during the month-old campaign in the volatile northwestern region, but the fighting has uprooted some 3 million people and triggered suspected reprisal attacks elsewhere in the country.

Chief army spokesperson Maj. Gen. Athar Abbas told reporters on a military-organized tour of the town of Mingora that it could take another two months of fighting to uproot the militants from their hide-outs in the lush, mountainous valleys of Swat and surrounding areas.

He cautioned, though, that even that timetable was "a rough estimate."

Earlier, Maj. Gen. Ijaz Awan, a senior commander in the eight-day battle for Mingora, said the military is gearing up for a fight in the nearby town of Kabal, where top Taliban leaders are suspected of being holed up.

"We have bottled them up very well, hopefully this will be a decisive battle here" in Kabal, said Awan. "Their deaths are vital to killing their myth."

The battle for Swat, launched in late April after the militants abandoned a peace deal that gave them control of the northwestern region bordering Afghanistan, is seen by Washington as a test of Pakistan's resolve against militants.

The United States strongly backs the campaign, and it has enjoyed broad support among Pakistanis tired of militant attacks in the country that have killed hundreds of civilians.

But that support may sour if civilian casualties turn out to be high or if the government is perceived to bungle the refugee crisis. The government must also contend with attacks elsewhere that officials say are an attempt to distract the military's attention from Swat.

One such attack was Monday night's ambush-kidnap of scores of students from a military cadet school in North Waziristan, near the Afghan border.

Paramilitary forces rescued 80 students and staff within hours, 45 others initially thought to have been saved were still captive.

Javed Alam, the director of studies at the school, Cadet College Razmak, told The Associated Press that some of the students had been allowed to briefly call their parents by their captors. No ransom or other demands were made, and the captors did not identify themselves, he said.

Abbas said the military learned Wednesday that not all the students were accounted for. "We thought it was over," he told AP.

Richard Holbrooke, the U.S. special envoy to Afghanistan and Pakistan, held talks in Islamabad on Wednesday with President Asif Ali Zardari. He was due to visit a refugee camp Thursday.

Holbrooke rejected a new claim by Osama bin Laden, in a newly issued recording, that U.S. was responsible for the Swat refugee crisis because Washington pressured the Pakistani military into carrying out the offensive.

"The idea that anyone is responsible for the refugee crisis other than al Qaeda and the Taliban and the other people that have caused such tragedy in Pakistan is ludicrous," Holbrooke said during a joint news conference with Zardari.

He also announced that President Barack Obama had asked Congress to approve US$200 million more in aid for the refugees, on top of $110 million already pledged.

"We believe that the actions taken by the Pakistani government and the military in recent weeks have been necessary, essential and have improved the situation" in Pakistan, Holbrooke said. "But the fighting is still going on, there is a lot more to go."

He said rebuilding damaged towns and resettling refugees would be critical for Pakistan's government. Power, water and gas remain cut in Mingora, the largest in the Swat region, and food is short. Officials are discouraging refugees from returning home yet.

"The people will have to be shown that this is not just a military operation, but one that has an enduring effect," he said.

During Wednesday's military tour through parts of Mingora, an AP reporter saw soldiers but little sign of civilian life among the 40,000 residents still there.

At a crossroads dubbed the "bloody intersection" by locals because the Taliban would leave mutilated bodies of victims there as a warning, there were signs of battle. Chunks of one multistory building were blown away, and security gates were torn off at least one storefront. Broken glass and bricks lay all around.

Awan said the military hoped about 2,500 police would return to Mingora by June's end, but that the army would probably have to stay in the Swat region for at least another year to fully secure it.