WASHINGTON (Yonhap News) ― The U.S. government is taking a longer-term approach in dealing with one of the most urgent and thorniest bilateral issues with South Korea ― Seoul’s push for enriching uranium and reprocessing spent fuel, according to an official here on Monday.

“The United States has been working with the Republic of Korea (South Korea) on the management of spent fuel and radioactive waste for over 30 years. The main current effort is a 10-year Joint Fuel Cycle Study, which is considering a variety of options for spent fuel management, including technologies related to nuclear waste disposal,” a State Department official told Yonhap News Agency on the condition of anonymity.

The official was apparently referring to the ongoing joint study on “pyroprocessing” and other ways of handling spent nuclear fuel. The 10-year study began in 2011.

South Korea argues that pyroprocessing is a proliferation-resistant technology. The U.S. claims the method, which has not been commercialized yet, is technically the equivalent of reprocessing.

Under a South Korea-U.S. nuclear agreement signed in 1974, South Korea is banned from enriching uranium and reprocessing spent fuel.

The agreement expires in March next year. Given the time for domestic procedures, Seoul and Washington need to reach a deal by the first half of this year.

Seoul hopes for Washington’s consent to its move to expand non-military nuclear programs for a stable supply of nuclear fuel and efficient management of nuclear waste.

South Korea, which produces 36 percent of its energy at 20 nuclear power plants, has to deal with more than 10,000 tons of nuclear waste at storage facilities that are expected to reach capacity in 2016.

It has also joined a club of nuclear plant exporters.

The U.S. acknowledges the significance of nuclear energy cooperation with South Korea.

“The United States welcomes the ROK’s emergence as a global nuclear energy leader and views a successor civil nuclear cooperation agreement, or ‘123 Agreement,’ as the foundation for further progress in this field,” the official said.

But U.S. officials maintain a lukewarm stance out of concerns about negative impact on its global nonproliferation campaign.

South Korea believes it is a matter of trust, while the U.S. does not want to set a negative precedent for future negotiations with other nations seeking nuclear energy partnerships.

An informed source said the two sides are struggling to move negotiations forward on revising the pact and a deal is unlikely before the informal June deadline.

If Seoul and Washington fail to strike a deal, they will face a lapse of the agreement or temporary extension of the existing version, both of which would carry considerable costs and risks.

Officials in Washington do not like openly talking about the sensitive issue at a time when the Seoul-Washington alliance is crucial.

According to the source, the U.S. government has yet to reach a consensus over whether some flexibility should be given in talks with South Korea, a time-honored blood ally.

Some officials call for Seoul to agree to what is known as the nonproliferation “gold standard” ― pledging not to enrich uranium or reprocess plutonium.

Others say Seoul’s safe operation of atomic energy plants and commitments to international obligations need to be considered.

The U.S. Congress is divided over the issue as well.

“Once the U.S. government reaches an internal agreement on the matter, South Korea will be able to expect full-fledged talks on the 123 agreement,” the source said.

Meanwhile, when South Korean Foreign Minister Yun Byung-se meets his American counterpart John Kerry in Washington on Tuesday, Yun may raise the issue.

“It would presumably come up on the ROK side,” State Department spokeswoman Victoria Nuland said at a press briefing.

She said she has no update for reporters on the South Korea-U.S. nuclear energy talks.

“I would guess, as it always does, when we are in Seoul, it will likely come up on the secretary’s trip,” she added. “This goes to the issues of ensuring that international standards are applied and all those things.”

Kerry is scheduled to travel to Seoul next month on his first regional tour as Washington’s top diplomat.