Story highlights US aircraft carriers finishing up exercises with Japanese, South Korean warships

North Korea warns UN chief that US is pushing region closer to nuclear war

Hong Kong (CNN) The presence of three US aircraft carriers off the Korean Peninsula is pushing the region closer to nuclear war, according to a North Korean letter to the UN secretary-general.

The three carriers, the USS Ronald Reagan, Theodore Roosevelt and Nimitz, and their multiship strike groups are finishing up four days of exercises Tuesday in the waters between South Korea and Japan.

It is the first time three of the 100,000-ton behemoths have sailed together in the Western Pacific in a decade. South Korean and Japanese warships have joined them during the exercise.

B-1B bombers and F/A-18 strike fighters fly over a Japanese carrier and the USS Theodore Roosevelt.

The exercises, which also have involved US B-1 bombers, help to constitute "the worst ever situation prevailing in and around the Korean Peninsula," Ja Song Nam, North Korea's ambassador to the United Nations, said in a letter Monday to the secretary-general.

The USS Ronald Reagan, Theodore Roosevelt and Nimitz and their strike groups conduct operations.

Washington "is now running amok for war exercises by introducing nuclear war equipment in and around the Korean Peninsula, thereby proving that the US itself is the major offender of the escalation of tension and undermining of the peace," the letter read.

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