Secretary of State John F. Kerry arrived in South Korea on Sunday armed with messages directed north of the 38th parallel at North Korea, which has sowed concerns with its recent actions at sea and in cyberspace.

Kerry was set to meet with Foreign Minister Yun Byung-se and President Park Geun-hye, and he planned to underscore the United States’ “ironclad commitment” to South Korea’s security, according to a senior State Department official.

His visit, though planned weeks ago, comes in the wake of fresh provocations from Pyongyang.

Earlier this month, North Korea fired what it claimed was a ballistic missile from a submarine, though some analysts doubt it was anything more lethal than a balloon. Concern about the mercurial temperament of North Korea’s leader, Kim Jong Un, grew when South Korea’s intelligence agency said last week that he had ordered the execution of his defense minister with an antiaircraft gun for the offense of sleeping during a meeting.

Kerry also plans to deliver a speech on Internet freedom and cybersecurity while in Seoul. South Korea is one of the most wired countries in the world, though it censors pornography and Web sites emanating from North Korea. President Obama has accused North Korea of being behind last year’s cyberattack on Sony Pictures in retaliation for a film, “The Interview,” a satirical depiction of an assassination plot against Kim.

Secretary of State John F. Kerry walks past an honor guard after arriving at Seoul Air Base on Sunday. (Saul Loeb/AFP/Getty Images)

Kerry has spent much of this month in the air, tending to issues that were put on the back burner earlier this year when he was consumed with negotiations over Iran’s nuclear program. This trip to Asia is his third overseas visit in two weeks, following swings through Africa and to Russia, where he met with President Vladimir Putin.

Kerry came to Seoul after two days of talks with top officials in Beijing. He repeatedly expressed Washington’s displeasure with China’s bid to extend its sovereignty by building man-made islets on top of shoals and reefs in the South China Sea.

For the most part, though, Washington and Beijing appeared to be talking past each other. After meeting with Kerry, the office of Fan Changlong, China’s top military officer, said he had told the top U.S. envoy that China’s islet-building was well within its rights.

“China’s determination and will to safeguard sovereignty and territorial integrity is unswerving,” Fan is said to have told Kerry, according to an account his office issued.

U.S. officials said that when Kerry met with Chinese President Xi Jinping, they discussed their mutual desire that the Korean Peninsula be rid of nuclear weapons.

In a news conference Saturday in Beijing, Kerry said he hoped an agreement to cut back Iran’s nuclear program and ease international sanctions would have a “positive influence” on North Korea, by demonstrating that relinquishing nuclear weapons can lead to economic improvements and an end to being considered an international pariah.

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