North Korean and U.S. negotiators began unprecedented talks in New York on Monday aimed at eventual diplomatic normalization that would end over half a century of animosity.

North Korean Vice Foreign Minister Kim Kye-gwan and U.S. Assistant Secretary of State Christopher Hill lead the working group negotiations that were established by a denuclearization agreement signed last month.

The U.S. side is hosting the two-day talks, which will continue over dinner Monday and through Tuesday at its U.N. mission.

The working group is a by-product of the Feb. 13 agreement by South and North Korea, the U.S., China, Russia and Japan, participants in the six-party talks, on phased denuclearization of the Korean Peninsula.

Under the accord, Pyongyang is required to shut down and seal its primary nuclear facility and eventually dismantle all of its nuclear weapons and programs. If it does so, it would receive political and economic incentives.

North Korea will hold another working group with Japan this week in Hanoi to discuss normalization of their ties.

Caution prevailed in Washington about the prospects for the talks, with the State Department saying it will "take some time" for them to fully bear fruit.

"It will be a matter of building up trust. It would be a matter of performance," department spokesman Sean McCormack said at his daily briefing.

"And today is just an initial discussion on that process," he said.

The working group is officially titled "normalization of DPRK-U.S. relations," referring to North Korea by its official name, the Democratic People's Republic of Korea.

But McCormack said the negotiations should not be characterized as "normalization talks."

The U.S. will talk to the North Korean delegation "about how the process might proceed regarding normalization," the spokesman said.

North Korea and the U.S. fought against each other in the 1950-1953 Korean War, which, technically, is not officially over.

The armistice signed at the end of the conflict has yet to be replaced by a peace treaty, and the U.S. maintains a military presence in South Korea as a deterrent against the North.

The Pyongyang regime has been on the U.S. list of state sponsors of terrorism since 1987, and any significant economic exchanges are barred under the U.S. Trading with the Enemy Act.

McCormack said both of these issues would be addressed at the New York sessions.

Vice Foreign Minister Kim Kye-gwan earlier said he is optimistic about the working group talks with the U.S.

"I think everything will go well," Kim told Yonhap as he headed out of his hotel to go to a closed-door seminar at the Korea Society in the morning.

Kim's aide echoed the overall optimism, saying the North Korean delegation had "nothing to feel bad about."

"Everything has been talked over with the U.S.," the aide said.

High-profile U.S. figures were seen going into the Korea Society seminar, including former secretaries of state Henry Kissinger and Madeleine Albright. Former U.S. Ambassador to Seoul Donald Gregg was also spotted.

Victor Cha, in charge of Asia at the National Security Council, and Sung Kim, head of the Korea Desk at the State Department, participated in the 24-person seminar.

Coming out of the four-hour event, participants declined to discuss details but described the atmosphere as "friendly" and "forthcoming."

Evans Revere, chief of the Korea Society, said all issues were addressed, including the North Korean nuclear agenda and Pyongyang's past abductions of Japanese citizens.

"Participants on both sides welcomed the opportunity to examine in detail matters of mutual concern which for some time had not been addressed bilaterally," a statement issued after the seminar said.

But skepticism lingered on whether North Korea will faithfully implement the Feb. 13 agreement, given its breach of a 2002 pact that froze Pyongyang's nuclear activities. That year, the U.S. accused the North of hiding a secret nuclear weapons program using highly enriched uranium (HEU), commonly referred to as the HEU program.

The New York Times reported Hill's delegation will provide Pyongyang with a "face-saving" way out of the HEU issue, citing ambiguity in the U.S. intelligence assessment on the program and thus allowing Pyongyang to simply explain that the HEU was a failed attempt to produce energy.

"I just don't know where that came from," said McCormack.

"We've said from the beginning, and it still stands that North Korea needs to come clean on all its nuclear programs, and that includes the HEU program."

Washington/New York, March 5 (Yonhap News)