North Korea failed in its highly vaunted effort to fire a satellite into orbit, military and private experts said Sunday after reviewing detailed tracking data that showed the missile and payload fell into the sea. Some said the failure undercut the North Korean campaign to come across as a fearsome adversary able to hurl deadly warheads halfway around the globe.

Defying world opinion, North Korea in recent weeks had moved steadily and fairly openly toward launching a long-range rocket that Western experts saw as a major step toward a military weapon. The launching itself of the three-stage rocket on Sunday, which the North Korean government portrayed as a success — even bragging that the supposed satellite payload was now broadcasting patriotic tunes from space — outraged Japan and South Korea, led to widespread rebuke by President Obama and other leaders, and prompted the United Nations Security Council to go into an emergency session.

But looking at the launching from a purely technical vantage point, space experts said the failure represented a blow that in all likelihood would seriously delay the missile’s debut.

“It’s got to be embarrassing,” said Geoffrey E. Forden, a missile expert at the Massachusetts Institute of Technology. “I can imagine heads flying if the ‘Dear Leader’ finds out the satellite didn’t fly into orbit,” he said, referring to the name North Koreans are obliged to use when speaking of Kim Jong-il, North Korea’s reclusive leader.