North Korea has sent a letter to United Nations Secretary-General Kofi Annan protesting a U.S.-led naval exercise off the coast of Japan.

North Korea says the exercise threatens global stability and could undermine six-nation talks on the communist state's nuclear ambitions.

Tuesday's "Team Samurai" drill in Sagami Bay, near Tokyo, was the twelfth in the American-led Proliferation Security Initiative, but the first to be held so near to the Korean Peninsula. The drills are aimed at training military personnel from various countries to intercept weapons of mass destruction at sea.

U.S. Navy Lt. Commander John Bernard, a Carrier Strike Group public affairs officer aboard the U.S.S. Kitty Hawk, says this week's exercise was not meant to send a message to any single country. "In other words, it is not saying 'hey, North Korea' it's saying 'no matter who you are, if you are thinking about WMD you should know that these countries have joined together and are committed to stopping it," said Mr. Bernard.

U.S. Undersecretary of State John Bolton, speaking in Tokyo on Wednesday, named North Korea along with Iran and Syria as, in his words, "the world's foremost proliferators of ballistic missiles and related technology to rogue states and hostile regimes."

Among the countries participating in this week's naval exercise, were Australia and France. Fifteen other countries, including Britain, Canada, India, Italy, Spain and Russia, attended as observers. China and South Korea declined an invitation to join the drill, apparently to avoid offending Pyongyang.

China and South Korea have been pushing the United States to ease its stance in six-party talks with North Korea to get it to dismantle its nuclear weapons programs.

North Korea on Friday also said the U.S. decision to reduce and relocate its troops in South Korea is a sign of a coming second war on the peninsula.

The official Korean Central News Agency, using inflammatory rhetoric typical of such dispatches, says "a nuclear holocaust to the Korean nation" is imminent.

The United States and South Korea on Tuesday signed an agreement under which more than 12,000 American troops will leave by 2008. U.S. forces will also vacate a base in Seoul and units will move south, away from the fortified Demilitarized Zone separating North and South Korea.