The former Soviet republic of Belarus says it will give up its stockpile of material used to make nuclear weapons by 2012.
The arrangement was announced on Wednesday on the sidelines of an international security meeting in the Central Asian nation of Kazakhstan by US Secretary of State Hillary Rodham Clinton and her Belarussian counterpart.
The announcement is a significant step forward in efforts aimed at keeping nuclear materials out of the hands of terrorists.
Clinton says Washington will provide technical and financial help to enable Belarus to dispose of its highly enriched uranium stocks. The amount of material was not mentioned but is believed to be enough to make at least several nuclear bombs.
Belarus in 1994 gave up the nuclear weapons it inherited in the breakup of the Soviet Union, but it retained its highly enriched uranium stocks.