N. Korea’s nuclear test raises tension, shows progress toward viable weapon

SEOUL — With its detonation Tuesday of a “smaller and light” nuclear device, North Korea moved closer to its top technological goal of building an atomic weapon small enough to mount on a long-range missile, a capability that would turn the secretive police state from a regional menace into a global one.

Security analysts cautioned that there is no immediate way to verify the North’s assertion that it has succeeded in manufacturing a smaller — or miniaturized — warhead. They added that Pyongyang sometimes makes exaggerated claims.

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Still, the latest nuclear test marks the clearest sign yet of the country’s intentions and signals a potentially contentious path in the months to come, as the North tries to test again and neighboring and Western countries try to dissuade it.

If the North wants to be fully confident that its nuclear devices work reliably, it will need to conduct subsequent tests — many of them, analysts say. Pyongyang hinted at such a path Tuesday, with its Foreign Ministry saying in a statement that the country was prepared to take unspecified “second and third stronger steps in succession” if the United States maintained its “hostile approach” toward the North.

That leaves officials in Washington, Seoul and Beijing scrambling to find a way to influence Pyongyang’s behavior — something they have not succeeded in doing.

The United States is limited in what it can do to change the North’s path, because the country is already so heavily sanctioned. In a statement Tuesday, Rep. Edward R. Royce (R-Calif.), chairman of the House Committee on Foreign Affairs, said President Obama should focus on “crippling the Kim regime’s military capabilities through stringent sanctions that tackle its illicit activities and cut off its flow of hard currency.”

But Washington, experts say, can do little beyond that without the cooperation of China, which is responsible for 70 percent of North Korea’s trade and which prefers the ruling Kim family to a united, and democratized, Korean Peninsula.

This time, China could react more harshly toward its traditional ally. Chinese leaders spent recent weeks trying strenuously to dissuade Pyongyang from the nuclear test, according to Western diplomats, who spoke on the condition of anonymity. Beijing’s inability to sway Pyongyang on the test points to growing exasperation in China with North Korean leader Kim Jong Eun and reflects a deteriorated relationship between the two countries that could have global consequences, the diplomats said.

The best indication of where North Korea and China stand will not be evident until the U.N. Security Council meets this week. Representatives of Western governments expressed hope Tuesday that Pyongyang’s open defiance of its powerful benefactor in Beijing would prompt China to support fresh penalties against the North’s leadership.

The test Tuesday was conducted in the face of strong opposition from the United States, and Obama said the North’s weapons program represented a “threat to U.S. national security and to international peace and security.”