Foreign Minister Yu Myung-hwan says North Korea is certain to have begun its uranium enrichment program more than a decade ago.

In an interview with Yonhap News Agency Wednesday, Yu said Pyongyang is likely to have begun enriching uranium shortly after it signed a deal with the United States in 1994 to abandon its nuclear ambitions, or at least in 1996.

Yu added, however, that little is known about the North’s nuclear program, including how much uranium and nuclear weapons it has produced or the program’s stage of development.

He added that the issue of uranium enrichment must be included on the agenda when the six-nation talks resume, in line with Pyongyang’s claim that it has successfully conducted experimental uranium enrichment.