— North Korea launched a long-range rocket Friday morning in defiance of repeated international protests, but it failed to reach orbit, breaking apart soon after the blastoff, U.S. and South Korean officials said.

The three-stage rocket — carrying a satellite that Pyongyang said was intended for weather observation — was fired from a launch pad in North Korea’s northwest at 7:39 a.m., but it quickly separated into several pieces and fell into the sea, South Korean officials said. A U.S. official, speaking on the condition of anonymity, said the rocket broke up about 11 / 2 minutes into the flight.

Many nations, including the United States, viewed the satellite launch as a cover for a long-range missile test, because it requires comparable technology.

A successful launch would have raised international concerns about North Korea’s weapons technology, marking a key step in its mission to build a weapon that can reach the United States, according to officials. But the failure of the Unha-3 rocket, coming after two previous unsuccessful satellite launches, suggests that the North still hasn’t perfected the delivery system for an intercontinental weapon.

“The fact that it failed suggests there’s a little more time before North Korea has the capability to strike the U.S. directly,” said Scott Snyder, a North Korea analyst at the Council on Foreign Relations.

Nonetheless, security experts point out that Pyongyang, with a proven stable of short-range missiles, can still cause chaos in the region, where the United States has numerous military bases.

By going ahead with the launch, North Korea sparked immediate international outrage, and it will probably face a U.N. Security Council statement censoring the launch, according to diplomats who spoke on the condition of anonymity. The council was scheduled to be briefed at 10 a.m. Friday.

North Korea is one of the most heavily sanctioned nations, and existing U.N. resolutions ban the North from conducting weapons tests using missile technology.

The U.S. government, which has tried a combination of engagement and sanctions in a fruitless effort to alter North Korea’s behavior, will not seek additional sanctions, U.S. officials said. Instead, Washington will push for stepped-up enforcement of existing U.N. resolutions, U.S. officials said.

“We have all the sanction authorities we need under existing U.N. resolutions and executive orders,” said an Obama administration official, who was not authorized to speak on the record.

North Korea had intended the launch as the centerpiece of a centennial celebration of the birth of founder Kim Il Sung.

After more than four hours of silence following the launch, North Korea’s state media admitted that the satellite did not reach orbit. That frankness contrasted with the North’s approach after two previous failed launches, which it portrayed domestically as being successful.

In a brief statement, the North’s news agency said that its “scientists, technicians and experts are now looking into the cause of the failure.”

Friday’s attempt was a “clear step backward,” said Peter Crail, a nonproliferation analyst at the Washington-based Arms Control Association. The first stage of the rocket dropped into the sea about 100 miles west of Seoul, according to the North American Aerospace Defense Command. The later

stages failed to fire and plummeted into the Yellow Sea.

The White House said in a statement that the North is “further isolating itself” by engaging in provocations, but added that President Obama is “prepared to engage constructively with North Korea” if it lives up to its international commitments and deals peacefully with its neighbors.

White House officials moved to claim some credit for the North’s failure, saying that sanctions have prevented the country from developing its technology, including an advanced electronic system for weapons guidance.

But Mitt Romney, the lead Republican presidential candidate, was critical of the administration.

“Instead of approaching Pyongyang from a position of strength, President Obama sought to appease the regime with a food-aid deal that proved to be as naive as it was short-lived,” Romney said in a statement.

In February, North Korea, under new leader Kim Jong Eun, reached a deal in which it pledged to observe a moratorium on weapons testing and to freeze parts of its nuclear program. In return, the United States agreed to provide 240,000 tons of food aid.

The deal fell apart just weeks later when Pyongyang disclosed plans to launch a satellite, the Kwangmyongsong-3. North Korea said it had a right to conduct the launch under an international space treaty, but U.S. officials said the launch violated the so-called Leap Day deal. By conducting the launch, U.S. officials said, the North will lose the food aid.

Security experts fear that the Korean Peninsula could remain tense for months, particularly if Pyongyang follows its satellite launch with an underground nuclear test — as it did in 2009.

Days ago, South Korean officials, citing satellite images, told reporters about new excavation activity at a nuclear site in the North. The images, officials said, indicated that the North was preparing for a third nuclear test.

Wan reported from Washington. Staff writers Craig Whitlock in Washington and Colum Lynch at the United Nations and special correspondent Yoonjung Seo in South Korea contributed to this report.