North Korea has claimed the U.N. Security Council would prove itself to be a "political tool" of the United States if it were to take issue with Pyongyang's recent submarine-launched ballistic missile test while ignoring joint military exercises between South Korea and the U.S.

The North's ambassador to the U.N., Ja Song-nam, made the claim in a letter sent to the Security Council president last week, calling the drills "real nuclear war games of aggression" aimed at "occupying Pyongyang" to remove the North's leadership.

The letter, dated May 26, was posted on the U.N. website Sunday.

"The recent underwater test-fire by the DPRK of a ballistic missile from a strategic submarine is a legitimate measure of a sovereign state to bolster up its self-defense capability against the provocative military maneuvers of the United States," the envoy said in the letter.

"The council will be proved to be a political tool of the high-handed and arbitrary practice of one permanent member" if it only takes issue with the submarine missile launch while ignoring the military exercises, he said.

Ja demanded the council convene an emergency meeting on the joint exercises.

The council can take up the matter only if there is a request from a council member. Last year, North Korea twice asked the Council to deal with the issue, but no formal discussions took place.

Pyongyang has long accused the U.S. and South Korea of plotting to invade the country and using their annual military exercises as part of preparations for it. But Seoul and Washington have rejected the claim, saying the annual maneuvers are purely defensive in nature.

The North's letter came after South Korea asked the Security Council's North Korea Sanctions Committee to look into the North's submarine missile test to determine whether it violated U.N. resolutions banning Pyongyang from any ballistic missile activity.

The committee reported to the council last week that it will launch an investigation.

On May 9, North Korea claimed it successfully carried out an SLBM test underwater, renewing tensions on the Korean Peninsula amid concern that the North's SLBM capability, if fully developed, would pose a serious threat because its mobile nature would make it very difficult to detect preparations for a launch. (Yonhap)