``This is a colossal failure of our intelligence-gathering system, perhaps the biggest one in recent years,'' Richard Shelby, an Alabama Republican, said. He would hold hearings as early as this week, some of them possibly in open session, he added.

Shelby said the failure of the CIA and other spy outfits to warn of test preparations had deprived policy-makers of the possibility of using diplomacy to head it off. ``We want to know why this happened, how this happened, who was asleep, why they were asleep.''