By Michelle Nichols

UNITED NATIONS (Reuters) - North Korea accused the United States of targeting it with anthrax and asked the United Nations Security Council to investigate Washington's "biological warfare schemes" after a live anthrax sample was sent to a U.S. base in South Korea.

Live anthrax samples, which can be used as a biological weapon, were inadvertently sent to Australia, Canada, Britain, South Korea and laboratories in 19 U.S. states and Washington, D.C., the Pentagon said recently.

"The United States not only possesses deadly weapons of mass destruction ... but also is attempting to use them in actual warfare against (North Korea)," Pyongyang's U.N. Ambassador Ja Song Nam wrote in a letter to the U.N. Security Council and U.N. Secretary-General Ban Ki-moon, which was made public Friday.

U.S. State Department spokesman Jeff Rathke, said Washington had seen the letter, and added: "The allegations are ridiculous. They don't merit a response."

U.S. investigators are trying to ascertain whether the shipments of live anthrax stemmed from quality control problems at the U.S. military base in Utah which sent them, Pentagon officials have said.

North Korea "strongly requests the Security Council take up the issue of the shipment of anthrax germs in order to thoroughly investigate the biological warfare schemes of the United States," Ja wrote in his letter, dated June 4.

He attached a statement from North Korea's National Defense Commission, which urged the world to consider the anthrax shipment "the gravest challenge to peace and a hideous crime aimed at genocide."

North Korea is under U.N. sanctions for carrying out nuclear tests and missile launches. In addition to an arms embargo, Pyongyang is banned from trading in nuclear and missile technology, and is not allowed to import luxury goods.

The U.N. Security Council also added the issue of human rights in North Korea to its agenda in December, after a U.N. Commission of Inquiry report last year detailed abuses in the impoverished Asian state that it said were comparable to Nazi-era atrocities.

(Additional reporting by Arshad Mohammed; Editing by Bernadette Baum)