The United States announced on Tuesday that it would grant political asylum to North Korea’s ambassador to Egypt, his brother, and their families. Officials said that American intelligence agents had spirited them out of Egypt and brought them to this country over the weekend.

The ambassador, Chang Sung-gil, is the highest-ranking North Korean to seek political asylum in the United States. While the Clinton administration said little publicly for fear of upsetting delicate negotiations with North Korea, senior officials described the defections as an intelligence bonanza for the United States.

As head of the embassy in Cairo, one of North Korea’s most important diplomatic postings, Chang was familiar with his government’s dealings in the Middle East, especially its sale of missiles and other arms to Egypt, Syria, and Iran, the officials said.

The sales to Iran, in particular, have been of concern to the United States and its allies in the region, including Israel.

The fact that Chang defected to the United States - and not to South Korea, as others have - means that the Central Intelligence Agency will be the first to interview him, without having to work through the filter of South Korea’s intelligence services.

“Egypt and North Korea have an arms-sales relationship that makes this defection important to the United States,” a senior official said, speaking on condition of anonymity. “He will have had access to important information on arms sales throughout the Middle East.”

Chang’s brother, Chang Sung-ho, also a diplomat, served most recently as the trade attache at North Korea’s mission in France. The ambassador’s wife is an actress who, one official said, had close ties with the leadership in Pyongyang, including North Korea’s top leader, Kim Jong Il. Officials declined to disclose her name, citing security concerns.

The State Department announced the defections one day before delegates from the United States and North Korea are to meet in New York for a third round of talks about missile proliferation.

In those talks, the United States has pressed North Korea to accept international restraints on exporting missiles and missile technology. American officials say they expect to discover at the talks on Wednesday whether the defections will produce any diplomatic fallout.

Just last week, the State Department announced that it had imposed new economic sanctions on North Korea for the “missile technology proliferation activities” of two companies. The two companies were accused of exporting components that could be used in missiles. The penalties are only symbolic, though, because the United States has no trade with North Korea.

The State Department’s spokesman, James Rubin, declined to provide more than the sketchiest details of the defections and the administration’s decision to grant asylum. He would not discuss how the diplomats had left Egypt.

He did say the episode should have little effect on the missile talks in New York or on the “four party” talks that the United States, China, and the two Koreas are to resume next month. Those talks are a forum for negotiating a formal peace treaty to end the Korean War.

“Nor do we see this as connected to some collapsing of the leadership or anything of that nature,” Rubin said, “again, bearing in mind the limited capabilities we have to assess what is going on in the North Korean government, and in North Korea itself.”