United States ready to protect Japan and South Korea against any attacks of North Korea 0304132.

The bottom line, very simply, is that what Kim Jong Un has been choosing to do is provocative, it is dangerous, reckless and the United States will not accept the DPRK as a nuclear state," the top American envoy told reporters after meeting with his ROK counterpart Yun Byung-se at the State Department, referring to a recent series of threats made by the DPRK under the leadership of Kim.

"And I reiterate again, the United States will do what is necessary to defend ourselves and to defend our allies, Korea and Japan," Kerry said. "We are fully prepared and capable of doing so. "

He described the 60-year alliance between the U.S. and ROK as one "critical" to American engagement in Asia. "It is a linchpin of peace and stability in the region," he added.

The DPRK said on Tuesday that it has decided to restart operations at its Nyongbyon nuclear complex, including a uranium enrichment plant and a 5MW graphite moderated reactor that had been "mothballed and disabled" under an agreement reached at the six-party talks in October 2007.

Tensions have been running high on the Korean Peninsula since the DPRK conducted its third nuclear test on Feb. 12 as a countermeasure against the joint military drills of the United States and the ROK.

The DPRK has also threatened to launch a preemptive nuclear strike for self-defense and unilaterally nullified the 1953 armistice that ended the Korean War.

The U.S. Navy was moving a sea-based radar platform closer to the Korean Peninsula in order to monitor military moves of the DPRK, including possible new missile launches, CNN quoted a Pentagon official as saying on Monday.