U.S. teams are searching and taking samples from sites in Afghanistan where the Al Qaeda terrorist network may have been building chemical or biological weapons, a top Pentagon official says. 

Marine Corps Gen. Peter Pace said U.S. forces have visited some, but not all, areas where Al Qaeda may have been making such weapons of mass destruction. Results of tests from those sites have not come back yet, Pace said Wednesday.

"That one place where the only vial that had English on it said 'anthrax' kind of gives you pause,'' said Pace, vice chairman of the Joint Chiefs of Staff. "We are going to have the analysis, and don't have that yet."

Sept. 11 attacks suspect Usama bin Laden, Al Qaeda's leader, has said his group has chemical, biological and even nuclear weapons. U.S. officials have said Al Qaeda probably has crude chemical or biological weapons but not a nuclear bomb.

U.S. planes have bombed sites that officials believe could have been used to produce chemical or germ weapons. U.S. airstrikes hit a laboratory in Kabul that worked with anthrax, for example. Scientists at the lab say they only made anthrax vaccines for livestock.

Two journalists killed in Afghanistan on Monday had reported finding what they believed were glass vials of deadly sarin nerve gas at an abandoned Al Qaeda camp southwest of Jalalabad, an eastern city near the border with Pakistan. At other sites abandoned by the Taliban or Al Qaeda, reporters have found guides to making chemical and biological weapons.

Defense Secretary Donald H. Rumsfeld visited special operations troops at Fort Bragg, N.C., Wednesday to thank them for their service. Special forces in Afghanistan have helped guide bombs to targets and given anti-Taliban forces advice and supplies.

"The success of the targeting has just improved so dramatically" since special forces landed in Afghanistan, Rumsfeld told the soldiers: "The air war enabled the ground war to succeed."

Airstrikes also have killed several Al Qaeda and Taliban leaders, such as Al Qaeda military chief Mohammed Atef, killed in a raid Nov. 14.

"There's one (leader) right now that is trying to get out of the country because his legs were badly damaged in an attack, a senior official," Rumsfeld said Wednesday on CBS' 60 Minutes II.

"We have had good luck in finding these folks and putting weapons on them."

Rumsfeld said the United States hopes to base AC-130 gunships in Uzbekistan, a former Soviet republic on Afghanistan's northern border. The airplanes are armed with rapid-fire cannons that rain down 2,500 rounds per minute.

Rumsfeld said AC-130s were not yet in Uzbekistan. He said the U.S. wants to use them to support anti-Taliban forces besieging Kunduz, the only northern city still under Taliban and Al Qaeda control.

The Pentagon probably will send up to 1,500 Marines into Afghanistan, perhaps this week, officials said on condition of anonymity.

They would come from one of two Marine Expeditionary Units based on ships in the Arabian Sea off the coast of Pakistan. Those troops are specially trained for quick raids, counterterrorism and urban warfare, as well as reconnaissance and more traditional forms of combat.

The Pentagon also announced Wednesday that U.S. Navy ships in the Arabian Sea would begin stopping and searching vessels that could be carrying Taliban or Al Qaeda leaders. The fleeing leaders would have to cross through Pakistan to the coast before getting on a ship, since Afghanistan is landlocked.

Pace said no ships have been chased, boarded or searched so far. He said the Pentagon did not have specific information indicating Taliban or Al Qaeda leaders would flee by sea, but said the military wanted to be ready for that possibility regardless.

Rumsfeld confirmed that a new Air Force spy plane — the high altitude, unmanned Global Hawk — has begun flying over Afghanistan this week for the first time. He said it was being operated as a demonstration model, since the aircraft is still in development and has never before been used in a real operation.