SEOUL (Reuters) - North Korea has sent a letter to the U.N. Security Council rejecting accusations from South Korea that it was behind the sinking of one of its neighbor’s navy ships, saying it was the victim of a U.S.-led conspiracy.

Military rescuers search for possible survivors of missing crew members of the Navy corvette Cheonan that sank on March 26, off Baengnyeongdo, an island near the maritime border with North Korea April 3, 2010. REUTERS/Korea Pool

The letter, addressed to the U.N. Security Council president from the North’s permanent representative to the body, followed the filing of a complaint by the South last week demanding action by the international community to deter further aggression.

A team of international investigators led by South Korea’s military said in May that a North Korean submarine torpedoed the corvette Cheonan on March 26, snapping the vessel in half in a blast and killing 46 sailors.

North Korea, through its official media, has already rejected the charge, saying it was a ploy by the South’s President Lee Myung-bak aimed at political gains for his conservative government.

“With time it is becoming clearer through military and scientific analysis that the ‘investigation findings’ by the U.S. and the South, which had been from their announcement subject to doubts and criticism, is nothing more than a conspiracy aimed at achieving U.S. political and military goals,” said the letter, signed by the North’s permanent representative to the U.N. Sin Son-ho and carried by the official KCNA news agency.

“If the Security Council goes ahead with discussions on the ‘investigation findings’ ... no one will be able to guarantee there won’t be grave consequences to peace and stability on the Korean peninsula.”

North Korea has driven tensions to new heights in recent weeks by threatening war if Seoul imposes sanctions. The mounting antagonism between the two Koreas has unnerved investors, worried about armed conflict breaking out in the region.

Many analysts say neither side is ready to go to war, but see the possibility of more skirmishes in a disputed sea border off the west coast or along their heavily armed border.

Despite the tense confrontation, the South said on Wednesday it had approved the shipments of baby formula for North Korean infants as a rare exception to the ban on trade, travel and movement of goods across their border.

The United States, the South’s biggest ally, said Seoul may not seek a full Security Council resolution because of rising tensions after the sinking of the Cheonan. Seoul said it would hold discussions with its allies to ensure action was taken.

Western diplomats say China, North Korea only real ally, will not tolerate new sanctions, while Seoul appears determined to have the council at least agree on some form of rebuke.