U.S. Secretary of State John Kerry says he and Foreign Minister Yun Byung-se exchanged various ideas about the revision of the South Korea-U.S. atomic energy agreement.

In a joint news conference after holding talks with Yun in Washington Tuesday, Kerry said he will meet with the South Korean foreign minister for follow-up talks on the atomic energy accord when he travels to Seoul next week.

Kerry said he is “very hopeful” that the issue can be resolved before President Park Geun-hye visits Washington next month.

Kerry made such remarks after being questioned whether he believes South Korea-U.S. relations will be hurt if talks on revising the energy pact fail to yield results.

The South Korea-U.S. atomic energy agreement was signed in 1974 and expires next year. South Korea and the U.S. have been holding negotiations to revise the deal since the end of 2010 but remain at odds over the issue of reprocessing spent nuclear fuel.

South Korea wants the right to reprocess spent nuclear fuel, saying the used fuel from its domestic plants will reach a saturation point by 2016. However, the U.S. is reluctant to agree due to proliferation concerns.

A government official in Seoul said there is no change in the U.S.’ stance over the energy pact.