North Korea surprised the United States by launching a three-stage rocket and, with lighter payloads, could be on the way to developing an intercontinental-range weapon, U.S. intelligence officials are telling lawmakers.

In a classified briefing Wednesday on Capitol Hill, the nation's top military and civilian intelligence officials told members of the Senate Armed Services Committee that they were closely examining the system launched by Pyongyang and studying whether lighter payloads might extend its range enough to reach the United States."The fact that they had a third-stage capability was not predicted by the intelligence community, and they are doing a reassessment," Sen. Chuck Robb, D-Va., said after a classified briefing by CIA Director George Tenet and Army Lt. Gen. Patrick Hughes, head of the Defense Intelligence Agency.

U.S. intelligence has concluded that the launch, though ostensibly intended to put a satellite into orbit, demonstrates continued North Korean efforts to develop intercontinental-range missiles. A key U.S. intelligence priority, according to a senior intelligence official, will be determining how small a payload might be used to enable the same type of rocket to propel a warhead more than 3,400 miles or far enough to reach parts of the United States.

The Aug. 31 North Korean rocket test was ominous, not only because of the rocket's multistage capability but also because the flight path was over Japan. Although the rocket's third stage failed to place its satellite payload into orbit, the rocket flew farther than North Korea's rocket program was thought capable of.