SEOUL -- South Korea's chief negotiator for civil nuclear energy pact with the United States was named as new ambassador to Russia, Seoul's foreign ministry said Thursday.

Park Ro-byug, South Korea's ambassador for nuclear energy cooperation, was nominated as ambassador to Russia, according to the Ministry of Foreign Affairs. He is expected to officially take office later this month.

Park served as the country's special representative for South Korea-US nuclear cooperation in the past four years.

Seoul and Washington agreed on April 22 to revise the 42-year- old civil nuclear energy cooperation accord after four and a half years of negotiations.

The revision was believed to open a door for Seoul to reprocess spent nuclear fuel as the country was allowed to continue pyro- processing research without consent from the United States.

The pyro-processing is seen as having less of proliferation risks as it cannot extract weapons-grade plutonium when reprocessing spent fuel.