South Korea and the United States signed a civilian nuclear energy cooperation agreement Monday, bringing a formal end to years of tough negotiations that had required the pushing back of an initial deadline, according to Yonhap News Agency.

South Korean Foreign Minister Yun Byung-se and U.S. Energy Secretary Ernest Moniz signed the revision to the 1974 nuclear cooperation pact that mainly stipulates South Korea's obligations in exchange for receiving technical support and other nuclear cooperation from the U.S.

Both Yun and Moniz called Monday's signing a "historic moment."

"We feel that this new agreement will upgrade our relations to a new height and -- thanks to this innovative, very much future-oriented agreement -- we will be able to work together in many new areas," Yun said during the ceremony at the Energy Department.

"This will get us securing a stable supply of nuclear fuel and manage spent fuel more efficiently and there are many areas where we can collaborate together in third countries. So this will give a big boost to Korean and American businesses as well," he said.

Moniz emphasized South Korea and the U.S. are strong advocates for nonproliferation objectives.

"This agreement solidifies that again as we enter a new phase of our cooperation," he said. The secretary also said that the U.S.-Korea partnership is an "absolute anchor" for peace and stability in the region and the partnership cannot be stronger.