The New York Times of the United States says North Korea showed a visiting American nuclear scientist earlier this month a vast new facility it secretly built to enrich uranium.

Stanford University professor Siegfried S. Hecker told the paper on Saturday that he had been “stunned” by the sophistication of the new plant, where he saw “hundreds and hundreds” of centrifuges that had just been installed in a recently gutted building that had housed an aging fuel fabrication center.

Hecker quoted North Korean officials as saying that two-thousand centrifuges were already installed and running.

The report said that the North's new uranium enrichment facility confronts the Obama administration with the prospect that the country is preparing to expand its nuclear arsenal or build a far more powerful type of atomic bomb.

The paper also said that whether the North's revelation of the uranium enrichment plant is a negotiating ploy by North Korea or a signal that it plans to accelerate its weapons program, it creates a new challenge for Obama at a moment when his program for gradual, global nuclear disarmament appears imperiled at home and abroad.

The paper also said the United States hurriedly began to brief allies and lawmakers on Friday and Saturday — and braced for an international debate over the repercussions.

U.S. Special Representative for North Korea Policy Stephen Bosworth embarked on a tour of South Korea, China and Japan on Saturday.

In a press statement, the U.S. State Department said that a pan-government delegation led by Bosworth has left for talks on the North Korean nuclear issue.

The delegates will arrive in Seoul on Sunday, visit Tokyo on Monday, Beijing on Tuesday and return to Washington on Wednesday.

The Foreign Ministry in Seoul says Bosworth will arrive in Seoul Sunday night and meet with South Korean nuclear envoy Wi Sung-lac the next morning. The U.S. envoy will then meet with Foreign Minister Kim Sung-hwan.

Bosworth's visit is thought to be aimed at sharing bilateral intelligence and preparing a joint response to North Korea's disclosure of its uranium enrichment facility.