Powell's evidence included aerial photos of what he identified as munitions bunkers, sites where Iraq tried to conceal chemical weapons, tapes of Iraqi generals ordering subordinates to "clear out" facilities and diagrams of mobile biological weapons labs, much of the evidence bolstered by information from defectors and informants.
Powell argued that the "irrefutable and undeniable" evidence left the Security Council no choice but to conclude that Iraq is flagrantly violating its demand in November that President Saddam Hussein disarm, and that to preserve its credibility it has to authorize the use of force to do the job.
"Clearly, Saddam will stop at nothing until something stops him," Powell said. "Leaving Saddam Hussein in possession of weapons of mass destruction for a few more months or years is not an option, not in a post-September 11th world.
"We must not shrink from whatever is ahead of us. We must not fail in our duty and our responsibility to the citizens of the countries that are represented by this body."
Powell's 80-minute presentation brought no immediate change in the position of council members, with the foreign ministers of veto-wielding France, Russia and China each insisting that the inspections continue and that all alternatives to force be explored.
Foreign Minister Dominique de Villepin of France, a pivotal force on the council, proposed that the inspections be beefed up with enhanced monitoring and a doubling or tripling of the number of inspectors, but would not rule supporting military action if Iraq ultimately failed to cooperate.
Russian Foreign Minister Igor Ivanov called for continued inspections but expressed support for the passage of one or more additional U.N. resolutions to increase the pressure on Iraq.
Most speakers looked ahead to this weekend's scheduled visit to Baghdad by chief inspectors Hans Blix and Mohamed ElBaradei as a new test of Iraqi behavior, expressing the hope that Powell's evidence will give the inspectors new ammunition to sway the Iraqi government.
But Iraq responded defiantly to Powell's presentation, with its ambassador to the United Nations, Mohammed al-Douri, saying that the secretary's "incorrect allegations" were based on "unnamed, unknown sources" and assumptions. The United States' intention, he said, was to "sell the idea of war" without any justification.
The quantity and variety of intelligence disclosed by Powell rivaled anything revealed during a public council session in decades, showing the sophisticated technical abilities of a superpower to monitor the actions of a recalcitrant, secretive state.
As anticipation built toward yesterday's meeting, many commentators compared Powell's appearance to the moment in October 1962 when Adlai E. Stevenson, President John F. Kennedy's U.N. ambassador, displayed spy plane photos of Soviet missile batteries in Cuba.
Unlike Stevenson, Powell did not reach for a single moment of high drama. Instead, using skills honed in his years as a military briefer, Powell gradually laid out his case, drawing on precise examples from what appeared to be a large store of damaging U.S. secrets about Iraq.
He said with conviction that the information came from "solid" sources. CIA Director George J. Tenet, sat just behind Powell in a sign that the often-fractious U.S. intelligence community stood behind Powell's presentation.
Summarizing the threat posed by Iraq, Powell declared: "When we confront a regime that harbors ambitions of regional domination, hides weapons of mass destruction and provides haven and active support for terrorists, we are not confronting the past, we are confronting the present, and unless we act, we are confronting an even more frightening future."
Powell played a tape of a conversation he said occurred Nov. 26, the day before inspections began, between a brigadier general in Iraq's Republican Guard and a colonel discussing what to do with "modified" vehicles that the inspectors might be looking for.