President Clinton said force is sometimes "the only answer" in a speech today at the Pentagon. If it does come to a military strike against Iraq, what weaponry will the U.S. use? Following a background report, Jim Lehrer talks to four retired military commanders about the possibilities.

The President's speech:

MARGARET WARNER: The United States and some of its allies have been building up their forces in the Gulf ever since last November's standoff between Iraq and the U.S. over United Nations weapons inspections.

In the Persian Gulf itself are two U.S. Naval aircraft carriers: the U.S.S. George Washington and the U.S.S. Independence. On their flight decks: Nearly 100 FA-18C and F-14 aircraft capable of dropping a variety of "smart" bombs; bombs that use electronics, computers, and sensors to reach their targets.

Accompanying the carrier battle groups in the Gulf are guided missile cruisers, frigates, destroyers, submarines, and support ships. A British carrier, the Invincible, joined these ships just two weeks ago. The U.S. warships are capable of launching Tomahawk Cruise missiles.

The current Tomahawks are faster and have greater range than those used in the 1991 Gulf War. They are almost more sophisticated. They can be programmed in minutes, rather than hours. And they are equipped with satellite guidance systems that make them more accurate, and less prone to misdirection due to smoke, sand, or fog.

The U.S. also has fighter aircraft positioned at ground bases in the region: at Incirlik Air Base in Turkey; Jabir Air Base in Kuwait; Sheik Isa Airfield in Bahrain; Prince Sultan Air Base in Saudi Arabia; and at a British base on the island of Diego Garcia in the Indian Ocean.

It's not clear, however, which of these countries will let the U.S. launch air strikes from its territory. Only Kuwait has agreed so far. Turkey has not said yes. Bahrain noted today it hadn't agreed either.

Saudi Arabia has made its reluctance clear, though it may let the U.S. use Saudi territory for support aircraft like AWACS early warning radar planes and airborne refueling tankers. Pentagon officials also said Saudi Arabia will let U.S. attack planes fly through its air space.

For now, there are nearly 100 different U.S. strike aircraft stationed in these countries--F-15, F-16, and F-117 Stealth jets, and B-1 and B-52 bombers. Many of the weapons carried on these planes are new, or considerably more sophisticated, than those used during the 1991 Gulf War. Among these new models is the laser-guided GBU-28.

This so-called "bunker-buster" bomb is the deepest-penetrating munition in the U.S. arsenal, designed for use against fortified underground concrete command posts.

Finally, the U.S. has 1500 combat ground troops in Kuwait, with another five to six thousand en route to Camp Doha there. Pentagon officials say the troops will deter Iraq from moving against the small kingdom.

The current U.S. ground forces pale in comparison to the several hundred thousand allied soldiers sent to the Gulf in 1991 to liberate Iraqi-occupied Kuwait.