North Korea appears to have launched a uranium enrichment program as a new way of building atomic bombs soon after its 1994 deal with the U.S. to dismantle its existing plutonium nuclear weapons program, South Korea said Wednesday.

Foreign Minister Yu Myung-hwan said in an interview with Yonhap news agency published Wednesday that the North appears to have launched its uranium enrichment program right after the 1994 agreement, or by 1996 at the latest.

Pyongyang last year said it had a uranium enrichment program, but did not say when it had started it.

Yu, who has expressed doubts in the past that North Korea will give up its nuclear program, did not give specific evidence as is common practice concerning intelligence matters. Yu's ministry confirmed his remarks.

If North Korea did launch their uranium enrichment program so soon after the 1994 deal with the U.S. it would underline the deceptive nature of the communist regime that has brandished nuclear threats to extract aid and concessions. It would also raise doubts whether Pyongyang has any intention to give up atomic ambitions.

"It appears the North started the uranium enrichment program right after the 1994 agreement or at least in 1996," Yu told Yonhap.

Atomic bombs can be made with highly enriched uranium or plutonium.

The 1994 pact between Pyongyang and Washington had defused an earlier nuclear crisis over Pyongyang's plutonium-based bomb program. Under that accord, the North agreed to freeze and ultimately dismantle its nuclear reactor in exchange for economic aid and diplomatic recognition.

The agreement fell apart in 2002 when the U.S. accused the North of running a secret uranium enrichment program, touching off the latest nuclear standoff.

North Korea had long rejected the uranium allegations. But in an attempt to further escalate tensions after its second-ever nuclear test in May last year, the regime claimed that it has such a program and succeeded in experimental uranium enrichment.

It has not said when that program started, and it was unclear whether Pyongyang would respond to Yu's allegation about the timing.

Yu said it is unclear how advanced that program is, how much uranium the North has enriched and how much of that has been turned into weapons.

Besides the uranium program, North Korea is also believed to have enough plutonium for at least half a dozen bombs.

Since 2003, the U.S., China, Japan, South Korea and Russia have engaged North Korea in six-party talks aimed at ending Pyongyang's nuclear programs, but they have been deadlocked for more than a year.

Last month, President Barack Obama's special envoy visited Pyongyang and the two sides agreed on the need to resume the stalled six-party talks. But the North did not make a firm commitment on when it would rejoin the negotiations, saying there are still unspecified differences to be resolved.

At the United Nations, China's ambassador, Zhang Yesui, on Tuesday urged the United States and North Korea to "seize the moment and take positive steps" so that six-party talks can resume quickly.

The ambassador, who took over the rotating presidency of the Security Council this month, called recent talks between senior U.S. and North Korean officials a "positive development."