Strategic Defense Initiative officials said their program has been scaled back and refocused, a move expected to cut costs and increase reliance on ground-based missiles to knock out nuclear warheads in space.

At a briefing Thursday to announce the latest success of the test program - a killer missile found and destroyed a dummy warhead in space - officials said the program President Ronald Reagan once touted as a potential umbrella-like protection for the nation will be focused on stopping a small launch of missiles or an accidental launch.The new design will be known as Global Protection Against Limited Strikes or GPALS.

In addition to space-based sensors, it will utilize between 750 to 1, 000 ground-based rockets that can rush into space and hit an approaching warhead, a reduction of about 50 percent in the number of rockets that had been planed.

And plans for space-based rockets to hit rising missiles from space have been cut to 1,000 interceptors, just 25 percent of the original goal.

The reductions will help cut the cost of the program and the emphasis on ground-based weaponry may help win the program more friends on Capitol Hill.

Additionally, it may allay some concerns that Moscow has voiced about it being and adjunct to a first strike weapon. A heavily effective missile defense could allow a nation to launch a first strike and use the SDI defense to knock out whatever response the enemy might be able to get off following an attack.

The latest experiment, the first of three, involved intercepting a dummy warhead about 160 miles above Earth.