North Korea is accusing the United States of targeting it with anthrax and wants the U.N. Security Council to look into they called America's "biological warfare schemes."

A letter from North Korea's U.N. ambassador to the council president and the U.N. chief, made public Friday, claims that the U.S. "possesses deadly weapons of mass destruction" that it is trying to use against them.

U.S. defence officials disclosed in late May that low concentration samples of live anthrax were shipped to labs in 19 states and four countries, including a U.S. military facility in South Korea.

The anthrax was supposed to have been killed with gamma rays before being shipped.

The spokesman for the current council president, Malaysia, said he had not heard of any initiatives on the council to take up the issue but would inquire further.

North Korea is highly sensitive to the U.S. military presence in South Korea, strongly objecting to annual U.S.-South Korean military exercises.

Ja Song Nam's letter says the shipment of live anthrax to South Korea means the U.S. "is attempting to use them in actual warfare" against his country.

State Department spokesman Jeff Rathke told reporters in Washington the allegations were "ridiculous," and didn't "merit a response."

Associated Press writer Bradley Klapper contributed from Washington.