U.S. and South Korean officials kicked off negotiations this week in the South Korean city of Daejeon, the sight of most of South Korea's nuclear research facilities.
The Yonhap News Agency reported Seoul expects to hold additional negotiations in April after this week's talks ended with little progress.
A 1974 bilateral nuclear treaty prohibits Seoul from enriching uranium or reprocessing spent nuclear fuel rods out of proliferation concerns. The South Korean government, however, wants the ban reversed because it wants to secure its nuclear fuel supplies.
Washington has expressed reservations out of concern for security on the Korean Peninsula.
Tensions between North and South Korea escalated last year after North Korea tested a nuclear device in February, its third since 2006.
U.S. Secretary of State John Kerry met Tuesday in Washington with South Korean counterpart Yun Byung-se to express his support for regional security in the face of the North Korean threat.
"We will not accept North Korea as a nuclear state nor as a nuclear-armed state, and nor will the international community abide by that," Kerry said in a statement.