New British troops arrived in the capital Monday just after complicated negotiations finally resulted in an agreement on how international peacekeeping forces will operate under Afghanistan's new government, officials said.

A convoy carrying about 70 British soldiers pulled into Kabul to reinforce an initial deployment that has been patrolling the capital and providing security to an interim government sworn in on Dec. 22.

Meanwhile, Marines in southern Afghanistan prepared to hand over its airport base to the Army's 101st Airborne Division. Army soldiers will assume operations at the encampment where 139 suspected Taliban or al-Qaida members are being interrogated by American military and intelligence officials in a makeshift jail.

The country's interim foreign minister, Abdullah, who uses only one name, said U.S. airstrikes are needed "as long as terrorist cells are in Afghanistan."

Abdullah told a news conference that Osama bin Laden may still be in the country - another incentive for foreign help in cleaning up the mess left by the former Taliban rulers. U.S. forces continue patrolling Afghanistan's rugged mountains, looking for the suspected terrorist and his followers.

The first deployment of peacekeepers - British Royal Marines - arrived days before the Dec. 22 inauguration of a six-month administration. But discussions had bogged down over the total number of needed troops and their duties.

Abdullah would not provide further specifics about the deal reached Sunday with representatives of the peacekeeping force, saying only that foreign troops will work with Afghans to provide security and are permitted to defend themselves.

Some within the interim Cabinet called for as many as 5,000 peacekeepers with a visible, and pro-active role. Defense Minister Mohammed Fahim wanted only 1,000 international troops performing peacekeeping duties with a low profile.

Without details of the agreement, it was not clear what concessions were made and by whom. Abdullah said only that some discussions took longer "than what was expected."

Other ministers in the week-old Cabinet have said the American bombing campaign, which helped defeat the Taliban and sent many al-Qaida fighters running, should stop to avoid more civilian casualties.

"Certainly we are concerned about that," Abdullah said. But bombing "should continue as long as it takes."

Some Taliban leaders are in custody, but "quite a few have disguised themselves and gone elsewhere," he said.

Speculation has run wild about bin Laden's whereabouts. Fahim said Saturday that bin Laden was believed to have slipped into Pakistan. Abdullah said they don't have clear information, "but he might be inside Afghanistan."

Though peacekeepers will initially be stationed in Kabul, the government also welcomes them in other cities, Abdullah said.

One sticking point may be the continued presence in Kabul of armed Afghan fighters. Under an agreement reached in Germany which empowered a temporary government, those soldiers are allowed only outside the capital.

However Abdullah said "Afghan soldiers will be based in military bases in and around Kabul."

Abdullah said he favors an Afghan war-crimes tribunal that would investigate abuses by the Taliban's repressive five-year regime. But he acknowledged prosecuting such cases would be difficult and time-consuming.

"It will take years and years," Abdullah said. "It's not a matter of days to draw up a list of war criminals."

He said the tribunal's mandate should not extend to before the Taliban took power. Many members of the new government were involved in the ill-fated administration that ruled Afghanistan from 1992-96, when factional fighting flattened entire neighborhoods and left an estimated 50,000 people dead.

In other developments, four soldiers were killed at Qul-e-Urdu, the main military base in Herat, during an accidental explosion that occurred as they stacked boxes of ammunition. An unknown number of people were injured, said Naseer Ahmed, spokesman for local warlord Ismail Khan.