Japanese lawmaker Antonio Inoki, right, shakes hands with North Korean official Ri Su Yongprior to their meeting in Pyongyang, North Korea, on Saturday. (AP)

North Korea’s nuclear program is directed at the United States, a close adviser to Kim Jong Un said after last week’s atomic test, according to a Japanese lawmaker who just returned from Pyongyang.

The warning came as two U.S. military B-1 bombers flew over the southern half of the peninsula in a show of force against North Korea, and top military brass and diplomats warned Pyongyang that the United States is prepared to take all steps to contain and punish the regime.

North Korea defied United Nations resolutions and international warnings by detonating its fifth and largest nuclear weapon Friday, declaring that it was a warhead that could be used to counter “the American threat.”

[Everything you need to know about the North Korean nuclear test]

Antonio Inoki, a former professional wrestler who now serves in Japan’s parliament, returned Tuesday from a five-day visit to Pyongyang saying that Japan need not worry about the North’s nuclear program.

North Korea has conducted its fifth nuclear test, on the day of an important holiday for the regime. The Washington Post’s Anna Fifield explains what that means. (Anna Fifield/The Washington Post)

“This is not directed at Japan. The nuclear development is toward the United States,” Inoki quoted Ri Su Yong, an elder statesman of North Korean foreign affairs who is particularly close to Kim, as saying.

Ri was Pyongyang’s ambassador to Switzerland when Kim, now the 32-year-old North Korean leader, attended school there. He served as foreign minister in Kim’s regime until May, when he was promoted further up the Workers’ Party ranks and became a full member of the Politburo and director of the party’s international relations department.

Inoki, who has tried to be a bridge between Japan and North Korea, told Japanese reporters who were waiting for him at the Beijing airport that he spent 90 minutes with Ri on Saturday, the day after the nuclear test. But these were the only remarks he made as he arrived at the airport.

[North Korea conducts fifth nuclear test]

His trip coincided with the nuclear test and followed provocative missile launches, several of which ended with landings within Japan’s air defense identification zone, earning harsh condemnation from Japan.

Although the missiles North Korea has been testing put only South Korea and parts of Japan and China within reach, many analysts agree that this is part of a larger program aimed at developing an intercontinental ballistic missile able to reach the U.S. mainland. The bigger goal is to attach a nuclear warhead to that missile, they say.

Pyongyang put out another dismissive statement Tuesday about the reaction to its nuclear test. “The U.S. and its followers are making much fuss, creating impression that a nuclear bomb was dropped in downtown Washington or Seoul,” the Korean Central News Agency said.

“Neither sanctions nor provocation nor pressure can ever bring down the position of the DPRK as a full-fledged nuclear weapons state, and highhanded political and military provocations of the enemies will only invite a merciless nuclear strike which will lead them to a final ruin,” the agency said, using the official abbreviation for North Korea.

[With each missile test, N. Korea inches closer to being able to reach the U.S. ]

In Seoul, U.S. and South Korean officials stepped up their warnings.

“North Korea’s nuclear test is a dangerous escalation and poses an unacceptable threat,” said Gen. Vincent K. Brooks, commander of U.S. Forces Korea, as two B-1B Lancers, which carry the largest payload of any U.S. bomber, flew over South Korea together with American F-16s and South Korean F-15Ks.

The bombers were moved to a U.S. air base in Guam in August as part of a buildup against North Korea, and they conducted a training exercise with Japanese fighter jets over the southern island of Kyushu while en route to the Korean Peninsula.

“Today’s demonstration provides just one example of the full range of military capabilities in the deep resources of this strong alliance to provide and strengthen extended deterrence,” Brooks said.

Separately, Sung Kim, Washington’s point man on North Korea, said after meeting his South Korean counterpart that the latest nuclear test has bolstered international resolve to hold the North accountable.

“We are, of course, working . . . to take additional significant steps, including new sanctions, to demonstrate to North Korea that there indeed are serious consequences for its unlawful and dangerous actions,” he said.

The U.N. Security Council, which imposed tough new sanctions after a nuclear test in January, also has condemned the test and vowed to respond.

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Today’s coverage from Post correspondents around the world