The North Korean Ambassador to the United Nations has sent a letter to U.N. Secretary-General Kofi Annan in protest of a U.S.-led naval exercise underway in Japan aimed at curbing the proliferation of weapons of mass destruction.

In the letter dated Tuesday, Ambassador Park Gil-yon argued that the multilateral military drill "constitutes a breach of the U.N. Charter and international law and order" and warned that the exercise posed a threat to global security and to prospects of resuming the six-way nuclear talks.

The North Korean diplomat claimed the naval exercise represents preparations for a preemptive attack against the Stalinist state.

The U.S.-led drill is part of the Proliferation Security Initiative (PSI). Some 60 nations lent support to this year's exercise, which was hosted by Japan earlier this week.