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WASHINGTON (AP) - Defense Secretary Leon Panetta says he's seen no outward sign that North Korea will follow through soon on its plan to conduct a third nuclear test.

But he says that doesn't mean much because Pyongyang has the ability to test in ways that are difficult to detect.

Panetta says the U.S. is "very concerned" with North Korea's announcement of a planned nuclear test - which he called "needlessly provocative."

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