The United States on Wednesday welcomed the new civilian nuclear cooperation pact with South Korea as a "major milestone" for the alliance and a demonstration of the two countries' "shared commitment to nonproliferation."

The two sides announced the revision to their 1974 nuclear energy cooperation pact in Seoul earlier Wednesday after more than four years of negotiations to reconcile Seoul's demand for the right to reprocess spent nuclear fuel and enrich uranium with Washington's concerns about proliferation.

The new agreement still bans Seoul from reprocessing and enrichment, but it opens the way for the Asian ally to begin research into a new technology for spent nuclear fuel recycling, known as "pyroprocessing," and to make low-level enriched uranium with U.S. consent.

The agreement will take effect after legislative and other reviews in both countries and will remain in force for 20 years.

"The agreement will mark a major milestone for the U.S.-ROK alliance and set the framework for reciprocal, dynamic and robust bilateral cooperation as global leaders in civil nuclear energy for years to come," a State Department official said on background.

"The agreement reaffirms the two governments' shared commitment to nonproliferation as the cornerstone of their nuclear cooperation relationship. The agreement is fully in line with U.S. law and long-standing U.S. nonproliferation policy," the official said.

South Korean officials have also hailed the agreement as a "win-win deal," saying it would give momentum to Seoul's efforts to secure a stable supply of nuclear fuel and expand nuclear plant exports. (Yonhap)