The United States has agreed to actively support South Korea seeking to export its nuclear power plants, government sources here said Friday, though the countries have failed, at least for now, to renew their bilateral accord on civilian nuclear cooperation.

The countries held three days of talks in the U.S. this week to revise their nuclear accord, known as the 123 agreement.

"There were three main areas of discussion in the negotiations, which were what to do with spent fuel rods, how to secure a stable supply of fuel for nuclear reactors and how to improve the competitiveness of the country's nuclear reactors for export," an informed source said, asking not to be identified.

"In this week's negotiations, there was significant progress on ways to enable overseas sales of (South Korean) nuclear reactors,"

the source added.

Other sources said U.S. support for overseas sales of South Korean nuclear power plants may include a provision of guarantee for a stable supply of fuel, which has long been considered the weakest point of South Korean reactors as the country has no means to supply nuclear fuel on its own.

Seoul hopes to be allowed to reprocess spent fuel through a new method called pyroprocessing, which, unlike conventional reprocessing technologies, will not produce weapons-grade plutonium.

Under the current agreement signed in 1974, Seoul is banned from reprocessing spent fuel or enriching uranium.

Seoul officials earlier said the sides may simply agree to extend the current agreement that is set to expire in March 2014. (Yonhap News)