Talks between South Korea and the United States over the issue of revising the Korea-U.S. Atomic Energy Agreement, initially scheduled to begin in the first half of 2010, will be postponed until after September, Seoul's Yonhap News Agency reported on Tuesday.

The nuclear accord, signed in 1974 and set to expire in 2014, requires South Korea to get consent from the United States to reprocess spent nuclear fuel as a measure against its possible use for military purposes.

Delay in negotiations comes as the deadly sinking of a South Korean warship in March has emerged as the most urgent issue facing the two nations.

"Given other pressing issues, discussions to renew the bilateral pact on the use of nuclear energy will be initiated in the latter half of this year," a high-level official related to foreign affairs was quoted as saying. "It seems most likely that the timing will be after September."

The official added that the two countries are currently running a joint study on the validity of pyroprocessing, but results haven 't come out yet.

Pyroprocessing is a new technology of electrolyzing spent nuclear fuel rods and extracting uranium and plutonium that can be reused as fuel. It is being developed under South Korea's initiative. Seoul maintains that pyroprocessing is necessary recycling because there is no chance of the technology being diverted for use in developing nuclear weapons.

South Korea and the United States were to embark on reform of the agreement sometime in June after the end of the Review Conference of the Nuclear Non-Proliferation Treaty (NPT) in May.