SEOUL - South Korea and the United States reached a deal Wednesday on nuclear energy pact after four and a half years of negotiations, Seoul's foreign ministry said Wednesday.

Seoul and Washington launched the negotiations in October 2010 to revise the atomic energy agreement, which took effect in 1973.

The agreement was originally terminated in March 2014, but the deadline was extended to March next year amid big differences on the revised pact.

The agreement has limited South Korea's ability to enrich uranium for power generation and reprocess spent fuel rod.

No further details have been made available. The two sides plan to initial the revised agreement at 4:15 pm local time in the headquarters of South Korea's foreign ministry.

South Korea, which is operating 23 nuclear power plants, depends on nuclear power for one third of its electricity needs.