Yesterday's Iraqi missile attacks on U.S. troops in Kuwait provided the first combat test of a Patriot anti-missile system that Pentagon officials say is much improved over the version used when the United States last went to war against Iraq 12 years ago.

A statement by U.S. Central Command credited Patriot interceptors with knocking down two missiles. But details about the attacks remained sketchy, preventing a full assessment of the Patriot's performance.

Reports varied, for instance, on the type of Iraqi missiles fired -- whether they were Scuds or shorter-range Ababil-100s or Al Samoud-2s. One Army air defense battalion commander in Kuwait said a Patriot interceptor failed to launch.

Also unclear was what type of Patriot interceptor actually scored the hits. According to the Central Command, two types were fired: the latest model and an older one.

For many Americans, images of Patriot interceptors appearing to blast Iraqi Scuds out of the sky were among the most memorable moments of the 1991 Persian Gulf War. U.S. officials touted the Patriots as emblematic of U.S. technological superiority, and missile defense advocates seized on the interceptors as evidence that a national anti-missile system also could work.

But the claims proved exaggerated as postwar analysis of television footage and videotapes showed the Patriot missiles had failed to intercept much of the time. More often than not, the analysis indicated, the Scuds, which were notoriously unstable, had themselves come apart in flight.

The revamped Patriot, known as Patriot Advanced Capability-3 (PAC-3), is two generations improved over the 1991 model. Instead of knocking down missiles by exploding in their flight paths, the new version is designed to ram enemy warheads.

This force of collision, which the original Patriots could not deliver, promises greater effectiveness against warheads packed with chemical or biological agents. It also is the basis of the missile defense system that President Bush intends to begin deploying in September 2004 to shield U.S. territory.

Although the PAC-3 system performed well in an initial series of flight tests, it floundered in field tests last year. Interceptors failed to fire in several cases, and when they did, they missed nearly as often as they hit.

Army officials had expected that the test failures would delay plans to move to full production of the weapon. But senior Pentagon officials decided to boost production anyway, without waiting for another round of tests. With only about 50 new interceptors in the Army's inventory, the Pentagon's leadership worried that U.S. stocks would be depleted quickly by a war with Iraq.

In January, Lockheed Martin Corp. which makes the PAC-3 interceptor, received a $341 million contract for continued production of the system. The contract called for delivering as many as 88 more missiles and associated ground electronics by 2005. Raytheon Co. is responsible for producing the missile's ground radar and command-and-control equipment.