Compounding the confusion and mixed messages of the North Korea nuclear crisis, the communist nation adamantly maintained Sunday that it had never told the U.S. it had established a secret weapons program.
"The claim that we admitted developing nuclear weapons is an invention fabricated by the U.S. with sinister intentions," South Korea's Yonhap news agency quoted North Korea's state-run newspaper, Rodong Sinmun, as saying.
Meanwhile, American envoy James Kelly, the U.S. assistant secretary of state, arrived in South Korea on Sunday in the hopes of finding a peaceful resolution to the intensifying crisis.
Kelly planned to meet South Korean President-elect Roh Moo-hyun, who believes diplomacy is the only solution. Kelly also planned to meet Foreign Minister Choi Sung-hong and two presidential security advisers -- Yim Sung-joon and Lim Dong-won.
Kelly will travel Tuesday to China, as well as Singapore, Indonesia and Japan.
In October, the United States said North Korea had admitted having a weapons program. That announcement touched off the latest standoff, which has led to North Korea's decision last week to withdraw from the landmark Nuclear Nonproliferation Treaty.
The United States believes North Korea has one or two nuclear weapons and could make several more within six months if it extracts weapons-grade plutonium from spent fuel rods at a reprocessing plant.
It wasn't clear if the threatening statement in the newspaper was aimed at influencing a new round of talks on resolving the crisis.
The newspaper blamed the United States for the current crisis and warned: "If the United States evades its responsibility and challenges us, we'll turn the citadel of imperialists into a sea of fire."
North Korea's communication on the existence of a clandestine nuclear weapons program has been laden with mixed messages.
In the October announcement, the United States said the North had admitted to having an atomic weapons program in violation of a 1994 accord, under which Pyongyang pledged to freeze operations at its nuclear facilities in exchange for energy supplies.
In response to the admission, the United States suspended fuel shipments, and the North said it would bring reactors at its Yongbyon nuclear facility back online.
After announcing its withdrawal from the treaty Friday, North Korea ratcheted up tensions even further by suggesting it might resume missile testing.
On Saturday, North Korean leaders vowed at a rally attended by 1 million people to "smash U.S. nuclear maniacs" in a "holy war."
But North Korean Deputy U.N. Ambassador Han Song Ryol told New Mexico Gov. Bill Richardson, a former U.S. ambassador to the United Nations, that the country had no intention of building nuclear bombs.
"He told me that in a dialogue with the United States, North Korea would discuss America's concerns over verifying its nuclear program. I think that's positive," Richardson said Saturday at the end of three days of meetings with the North Koreans.
Also Saturday, a North Korean official said its nuclear plant north of Pyongyang was ready for operation.
The threat of new missile tests came from the North's ambassador to China, Choe Jin Su, who said tests could resume if U.S. relations don't improve.
New tests would be the first since 1998, when North Korea shot a missile over Japan into the Pacific. Pyongyang later set a moratorium on tests which was to last into 2004.
Another official left open the possibility of the North reprocessing spent fuel rods from its nuclear reactor to make atomic bombs. Son Mun San, who oversees Pyongyang's relations with the U.N. International Atomic Energy Agency, said in Vienna the reprocessing plant now stands in a state of "readiness."
Since the nuclear standoff resumed, the North has removed seals placed on one of its nuclear facilities by IAEA monitors and expelled two U.N. inspectors.
South Korea vowed again Sunday to pursue a diplomatic solution, after National Security Adviser Yim Sung-joon returned from a visit to Washington and Tokyo.
"The government's consistent position is that it will do its best to resolve the North Korean nuclear issue peacefully through diplomacy," Yim told the Yonhap news agency.
During a visit to Russia that ended Sunday, Japanese Prime Minister Junichiro Koizumi urged North Korea to rescind its decision to pull out of the treaty.
"That is what's best for North Korea, for the international community," he said. "And this is true for the United States as well."
The Associated Press contributed to this report.