The U.S. special envoy for the Democratic People's Republic of Korea (DPRK) Monday called for a calm response to the DPRK's reported pursuit of a uranium enrichment program, saying the U.S. government knew of it beforehand.

"We've known about this for some time," Stephen Bosworth said in a meeting with South Korean Foreign Minister Kim Sung-hwan, according to local media. "It's a very unfortunate development, but it's not a crisis," he added.

The meeting came after The New York Times reported Pyongyang showed U.S. nuclear scientist Siegfried Hecker, who recently traveled to the DPRK, a vast, new plant to enrich uranium with " hundreds and hundreds" of centrifuges installed. However, there has been?no comment from Pyongyang on the report so far.

In a press briefing after meeting with Kim, the U.S. envoy said that if the facility has indeed been built, it would be a violation of U.N. Resolution 1874.

"This is obviously a disappointing announcement... It is also another in a series of provocative moves," Bosworth told reporters.

However, he said it is not a crisis, "We're not surprised by this", he added, noting that Washington has been "watching and analyzing the (DPRK's) aspirations to produce enriched uranium for some time."

While the newly disclosed nuclear facility in the DPRK poses a challenge, it does not mean the U.S. policy toward Pyongyang is a "failure", he said.

"We're not throwing our policy away," he told reporters, pledging to "refine" approaches to the DPRK. "We have to incorporate this now into our strategy as we move forward," he said.

The U.S. envoy said close cooperation among parties involving in the six-party talks is needed to deal with the latest development.

It is "fundamental we deal with this in close coordination with major countries", Bosworth said.

He also expressed his hope for the eventual resumption of the long-stalled multilateral nuclear disarmament forum, but noted at the same time that Pyongyang should show its sincerity on it.

On his part, South Korean Foreign Minister Kim Sung-hwan agreed that the reported situation in the DPRK is?"not a crisis", noting that Seoul and Washington need more "intelligence and analysis on what is the reality of the program" in the DPRK.

Earlier in the day, Bosworth also sat down with his South Korean counterpart Wi Sung-lac, Seoul's top representative for six- party talks over denuclearizing Pyongyang, to discuss disclosed centrifuges and the DPRK's apparent move to build light-water nuclear reactor.

DPRK's leading official newspaper Rodong Sinmun said last week that Pyongyang is ready for the resumption of the six-party talks, but the United States and South Korea have effectively blocked it by setting preconditions.

Bosworth arrived in Seoul late Sunday as part of a quickly three-nation Asian swing. He is scheduled to visit Tokyo and Beijing before returning home on Wednesday.