South Korea called for the United States to approve it undertaking "peaceful" enrichment of uranium and reprocessing of spent nuclear fuel, a government think tank said Monday, as little progress has been made in bilateral negotiations to revise the countries' nuclear accord. Under a 1974 accord with the US, South Korea is banned from enriching uranium or reprocessing spent nuclear fuel. The allies have held five rounds of formal negotiations since 2010 to rewrite the bilateral nuclear cooperation treaty, which expires in 2014. South Korea, a major nuclear energy developer, wants the US to allow it to adopt a proliferation-resistant technology for enriching uranium and reprocessing spent atomic fuel from its 22 nuclear power plants, but Washington has been reluctant to do so. In the face of growing nuclear waste stockpiles and its ambition to become a global power in the civilian nuclear industry, South Korea hopes to adopt the so-called pyroprocessing technology, which leaves separated plutonium, the main ingredient in making atomic bombs, mixed with other elements. South Korea wants the US to allow it to use the new technology because it has to deal with more than 10,000 tons of nuclear waste at storage facilities that are expected to reach capacity in 2016, South Korea's news agency (Yonhap) reported. Reflecting Washington's firm stance to keep restricting South Korea from having uranium-enrichment technology, Gary Samore, arms control coordinator at the White House National Security Council, told reporters in July that there is no need for Seoul to enrich uranium.