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In an escalating bid to strangle the Taliban in its last bastion in Afghanistan, U.S. Marines moved Tuesday to seal off escape routes from the besieged southern city of Kandahar while Afghan tribal forces fought Taliban troops.

As the battle raged in the south, hundreds of anti-Taliban fighters piled into trucks in pursuit of Osama bin Laden and an estimated 1,200 Al Qaeda forces believed hiding in the White Mountains near the eastern city of Jalalabad. A senior Northern Alliance commander said that in the past two days, U.S. air strikes in and around bin Laden’s suspected lair in the Tora Bora cave complex have killed 12 members of the Al Qaeda terrorist network.

Anti-Taliban leaders also claimed that bin Laden’s top lieutenant, Ayman al-Zawahiri, and his finance chief, Ali Mahmoud, had been killed or injured by U.S. bombs. None of their claims could be independently verified.

“This fight has just begun,” Air Force Gen. Richard Myers, chairman of the Joint Chiefs of Staff, said in Washington, adding that U.S. bombers continued to strike targets in Kandahar, near Jalalabad in the east and around Mazar-e Sharif in the north.

A U.S. Special Forces soldier was wounded in combat near Kandahar on Tuesday, military officials said. The wounds were not life-threatening, the Pentagon said.

Unconfirmed reports stated that Taliban leaders trapped in Kandahar had contacted Afghan tribal leaders, seeking either terms of surrender or the means to escape the city.

Military developments in recent days suggest the nature of the U.S.-led anti-terrorism campaign has been redefined. Instead of getting the Taliban and bin Laden on the run–the campaign’s original stated objective–the effort now appears to be isolating the enemy in relatively small areas and surrounding it.

Al Qaeda’s leaders are believed to be in rugged mountains near the Pakistani border. A few appear to have escaped U.S. forces and may now be in lawless border regions of Iran and Pakistan, according to a U.S. intelligence report.

The tribal forces assaulting Tora Bora have only tenuous ties to the U.S. military but are getting some assistance from the CIA. A small contingent of U.S. special forces were helping about 1,500 anti-Taliban Afghans in the hunt for bin Laden on Tuesday, according to a Pentagon official. The special forces were there to identify targets for air strikes, the official said.

Deal near in Bonn talks

Off the battlefield, Afghanistan moved closer to a unified interim government. Rival Afghan factions meeting near Bonn were on the verge of signing an accord setting up a 29-member interim Cabinet.

“Now we have a road map to a free and independent Afghanistan,” said Ahmad Fawzi, a United Nations spokesman, But, he cautioned: “Anything can go wrong.”

President Bush said that once the military objective in Afghanistan has been achieved, U.S. forces might carry the fight against terrorism to other countries. In an interview for the ABC News program “20/20” that is scheduled to air Wednesday, the president said “there may be a need to use military troops elsewhere.”

“I just want the American people to know that we’re keeping all options on the table,” said Bush, who has in recent weeks suggested U.S. forces might carry out pre-emptive strikes against Al Qaeda and other terrorist groups outside Afghanistan.

Frustration in Mazar-e Sharif

The movement of Marines around Kandahar reflects the new strategy toward the Taliban and Al Qaeda. Containing those forces’ movements has become a key mission of the U.S. Marines in southern Afghanistan. Failure to contain the enemy has frustrated U.S. special forces in the north near Mazar-e Sharif, senior military officials said Tuesday.

There, enemy fighters have slipped through seams in the lines of U.S.-backed rebel forces, or negotiated their way to freedom, only to pop up with weapons in other towns and sparking new battles. Some of those Taliban and Al Qaeda fighters have re-emerged in provinces near Mazar-e Sharif.

On Tuesday a member of a U.S. special forces team supporting opposition fighters outside Kandahar was shot through the shoulder and flown to a military hospital in neighboring Pakistan. A spokesman for the U.S. Central Command said the soldier was listed in stable condition.

`Americans . . . at risk’

At the Pentagon, Defense Secretary Donald Rumsfeld said the success that U.S. forces and Afghan rebel groups have had in pushing the formerly ruling Taliban and its Al Qaeda militants into pockets does not mean the war is almost over.

“While the amount of real estate they control becomes smaller, we’re by no means approaching the end of the campaign,” Rumsfeld said. “And as we move from the cities to searching caves and shadows, Americans will of course be increasingly at risk.”

As to the exact location of bin Laden, Pentagon officials say they have educated guesses, but they cannot be sure he is still in Afghanistan.

“We believe we are reducing the amount of real estate that those folks have to move around on,” Rumsfeld said. “The problem with that is, Afghanistan’s got long, porous borders. . . . In the event that he decides to flee, we’ll just have to follow him where he flees.”

U.S. Marines get help

Some 1,300 Marines, a force that could grow to 1,500 in a few days, have been joined by British and Australian ground forces in the area around Kandahar, the Taliban’s southern Afghan stronghold.

“They are prepared for engagements,” Myers said. “They’re a robust fighting force and they’re absolutely ready to engage if that’s required.”

The Marines have a threefold mission: add to the pressure that U.S.-backed forces are putting on the estimated 8,500 Taliban fighters in Kandahar; prevent Taliban reinforcements from entering the city; and prevent Taliban leaders from exiting.

Rumsfeld said there were no immediate plans to send the Marines into the battle for Kandahar, the Taliban’s spiritual home base.

Taliban re-emerging in north

In Baghlan, northwest of the capital, Kabul, some 500 to 1,000 Taliban fighters remain entrenched, according to the U.S. defense official. In the town of Balkh just west of Mazar-e Sharif, some 2,000 to 2,500 Taliban and possibly Al Qaeda fighters remain armed and dangerous.

Some of these may have been fighters who gave up their weapons or surrendered, only to disappear into the general population and emerge later with new arms. Others had been freed by the U.S.-backed Northern Alliance as part of a negotiation that led to the alliance’s capture of Mazar-e Sharif.

“Some in Balkh were allowed to depart [Mazar-e Sharif] as part of the surrender, only to return to fight again,” the defense official said. “That’s frustrating.”

Relations between the U.S. and its Afghan allies are one of the touchier aspects of the campaign. Rumsfeld described the links with the Northern Alliance as solid. Less certain are the motives and aims of opposition groups in the Jalalabad area, closest to where bin Laden might be hiding.

Rumsfeld: Goal is clear

One reason for the large U.S. presence in southern Afghanistan around Kandahar is the Pentagon’s doubts that Afghan fighters would be able to prevent Al Qaeda and Taliban leaders from escaping.

Asked about statements by opposition leaders suggesting they may not immediately turn over to the U.S. anyTaliban and Al Qaeda leaders they may capture, Rumsfeld was blunt.

“We are there to capture or kill the Al Qaeda and foreign invaders in Afghanistan who are terrorists, and we are there to change the Taliban leadership,” Rumsfeld said. “Everyone that we are assisting knows precisely why we’re there.”

If an opposition leader refused to hand over a senior Al Qaeda or Taliban captive, Rumsfeld said, “obviously, our relationship with them would change.”

Tribune staff reporter Tim Jones in Chicago and Tribune news services contributed to this report.