A revised nuclear deal between South Korea and the United States for the next 20 years goes into effect Wednesday, according to the South Korean government.

The earlier treaty, reached in 1972, is now replaced with the revised one which will allow the South to gain the ability to enrich uranium. The Asian country will be able to negotiate with U.S. authorities in future for producing non-weapons-grade nuclear fuel, The Associate Press reported.

South Korean foreign minister exchanged documents with the U.S. ambassador to South Korea, the South Korean foreign ministry said in a statement.

In April, the two countries agreed to sign a new nuclear deal to approve the republic’s nuclear research after nearly five years of negotiations. However, U.S. authorities, worried about the nuclear future of Northeast Asia, did not allow Seoul to produce its own fuel.

“The U.S. held to its nonproliferation principles but did so in a way that recognizes South Korea’s robust and highly developed nuclear program,” the Wall Street Journal quoted Mark Fitzpatrick, director of the nonproliferation and disarmament program at the International Institute for Strategic Studies in London, as saying.

The South said that nuclear fuel would help the country reduce import costs. At the same time, it will help Seoul export nuclear reactors. The Asian republic’s plan is to reprocess used fuel so that it can reduce nuclear waste.

The reason behind the opposition against such activities by the United States is that countries can use the same technologies to produce weapons-grade nuclear fuel. It Washington supports such programs for South Korea, it may send a wrong signal to the North which is has an active nuclear weapons program.