Tucked inside Congress' new blueprint for U.S. intelligence spending is a highly classified and expensive spy program that drew exceptional criticism from leading Democrats.

In an unusually public rebuke of a secret government project, Sen. Jay Rockefeller of West Virginia, the senior Democrat on the Senate Intelligence Committee, complained Wednesday that the program was ''totally unjustified and very, very wasteful and dangerous to the national security.'' He called the program ''stunningly expensive.''

Rockefeller and three other Democratic senators (Richard Durbin of Illinois, Carl Levin of Michigan and Ron Wyden of Oregon) refused to sign the congressional compromise negotiated by others in the House and Senate that provides for future U.S. intelligence activities.

The rare criticisms of a highly secretive project in such a public forum intrigued outside intelligence experts, who said the program was almost certainly a spy satellite system, perhaps with technology to destroy potential attackers. They cited tantalizing hints in Rockefeller's remarks, such as the program's enormous expense and its alleged danger to national security.

A U.S. panel in 2001 described American defense and spy satellites as frighteningly vulnerable, saying technology to launch attacks in space was widely available. The study, by a commission whose members included Donald H. Rumsfeld prior to his appointment as defense secretary for Bush, concluded that the United States was ''an attractive candidate for a Space Pearl Harbor.''

Sending even defensive satellite weapons into orbit could start an arms race in space, warned John Pike, a defense analyst with GlobalSecurity.org, who has studied anti-satellite weapons for more than three decades. Pike said other countries would inevitably demand proof that any weapons were only defensive.

''It would present just absolutely insurmountable verification problems because we are not going to let anybody look at our spy satellites,'' Pike said.