(CNN) -- The United States will talk to North Korea, but only if the country gets serious about negotiating the end of its nuclear weapons program, Secretary of State John Kerry said Friday during a visit to South Korea, a key U.S. ally. "North Korea will not be accepted as a nuclear power," Kerry said after arriving in Seoul. His trip to South Korea -- part of an Asian swing that also includes North Korean ally China -- came a day after a Pentagon intelligence assessment surfaced suggesting North Korea may have developed the ability to fire a nuclear-tipped missile at its foes.
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NEW: U.S. says it "stands vigilantly by" South Korea
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NEW: North Korea denies responsibility for hacking South Korean computers in March
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U.S. will talk to North Korea, but Pyongyang has to talk giving up nukes, Kerry says
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Ballistic missiles may be able to carry nukes, a U.S. defense intelligence assessment says
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Kerry now plans to visit @placeholder and tell leaders there that Pyongyang, as one senior administration official said, is "putting China's own interests at risk."
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On Thursday, @placeholder briefly raised a missile into an upright firing position, stoking concerns that a launch was imminent, a U.S. official told CNN.
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@placeholder this week accused the North of carrying out the March 20 attacks.
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South Korea this week accused the @placeholder of carrying out the March 20 attacks.