SEOUL (REUTERS) - South Korea and the United States reached a deal on Wednesday to revise a 40-year-old agreement that has limited South Korea's ability to enrich uranium for nuclear power generation and to reprocess spent fuel, the foreign ministry in Seoul said.

No further details about the revised agreement were immediately available. Officials of the two countries are scheduled to initial the revised agreement later on Wednesday in Seoul, the ministry said.

South Korea operates 23 atomic plants that provide one-third of the country's power needs, and has pushed for greater liberty to manage its nuclear fuel and sought to revise the original pact with Washington so it can reprocess spent fuel.

Nuclear reactors add a total of 750 tonnes of spent fuel every year to the 13,300 tonnes that filled 71 per cent of its wet and dry storage capacity as of 2013, according to operator Korea Hydro and Nuclear Power Co Ltd, owned by state-run Korea Electric Power Corp.

Reprocessing is a thorny issue diplomatically because of concerns about nuclear proliferation, especially on the Korean Peninsula, where North Korea has defied efforts by the international community and pushed to develop nuclear weapons.