EGLIN AIR FORCE BASE, Fla. (AP) _ Weapons developers are putting the finishing touches on what may be the final element needed to destroy the chemical and biological weapons Iraq is suspected of concealing.

Known as an ``agent defeat material,'' it would replace conventional explosives in new ``smart'' weapons, already aimed at Iraq, that are more accurate and lethal than those used in the 1991 Persian Gulf War.

These weapons include all-weather, satellite-guided bombs and missiles designed to penetrate hardened bunkers where Iraqi leader Saddam Hussein may be hiding chemical and biological agents.

Similar to rocket fuel, the new material would create a flash fire with temperatures measured in thousands of degrees to incinerate the agents before they can spill from the punctured bunkers, said Frank Robbins, director of the Air Force's Precision Strike System Program Office.

``You want to come up with a defeat mechanism that is effective, but not effective to the point that collateral damage occurs,'' Robbins said. ``This isn't a big fire, it's a hot fire. And it's a precise, hot fire. Intentionally, we don't want to blow things up.''

The Air Force tested the material Jan. 14 on a bunker at this Florida Panhandle base.

``The test indicated that temperatures and pressures we achieved actually exceeded what we were looking for,'' Robbins said. ``It was a couple of days before you really needed to go into that room because the temperatures it creates are so hot.''

The material is still under development, but Robbins intimated it could be available on short notice if Iraq continues to bar United Nations inspectors from suspected weapons sites.

``We can move quickly when we're asked to,'' Robbins said, citing the GBU-28, a mammoth 5,000-pound bunker-busting bomb created during the Gulf War.

It took Eglin, the Air Force's primary weapons development and test center, only 28 days to fashion the laser-guided bomb from surplus Army cannon barrels. One of the weapons penetrated a very deep hardened target in the waning days of the war.

The agent defeat material is the latest of several advances the Air Force has made in bunker-busting weapons since the Gulf War.

The puncturing capability of the GBU-28 as well as lighter weapons, many of which could be loaded with the agent defeat material, have been doubled by a new warhead, the Advanced Unitary Penetrator.

It has an aluminum covering that shears off upon impact to reveal a rod smaller in diameter but weighing the same as previous warheads because it is made of a denser steel alloy.

``Given those parameters, if you hit the earth at the same velocity it will go twice as far,'' Robbins said.

Two new fuzes are designed to make sure weapons explode only after they have pierced deep inside a bunker or building. The Joint Programmable Fuze, already in the field, uses a timer to delay the explosion.

The Hard Target Smart Fuze has both a timer and a sensing device that can count how many floors, walls or earthen barriers have been penetrated and explode the warhead upon reaching the desired number.

Like the agent defeat material, this fuze is in development but could quickly find its way into combat.

``We have what we call `leave-behind assets' out of our initial development effort we kept in case we needed them for operational purposes,'' Robbins said. He declined to say how many exist.

``Today would be a good day for some of these weapons,'' Robbins said as rain fell from a dark sky outside his office. ``And that would not have been the case in the Gulf War.''

During that conflict, rain, clouds, haze, smoke and other atmospheric factors prevented the use or hampered the accuracy of television and laser-guided weapons.

``We've had TV seekers for a long time, but as you can see on even commercial television it has improved dramatically _ the resolution and how much light is required,'' Robbins said. ``We can go in pure darkness with high resolution.''

Satellite navigation, called GPS for Global Positioning System, is another improvement. Commercial aircraft and ships, even pleasure boaters and hikers, use GPS, but the military system is much more accurate than its civilian counterpart. Many weapons use a combination of guidance systems.

``It would hit within this room if you didn't have anything other than GPS,'' Robbins said, seated at a small table in his office about the size of a typical motel room. ``And if you use the other guidance part you'll hit someplace in the center of this table.''

Such precision also helps pilots avoid enemy air defenses because they can launch missiles or drop glide bombs from greater distances and head for home while the weapons make their way to their targets.

The immediate focus is on destroying chemical and biological weapons in hardened bunkers, but other contingencies are being considered, although the Air Force isn't ready to disclose details.

``There are other things being looked at ... to defeat it in open storage,'' Robbins said. ``We are looking at all storage scenarios.''