A senior U.S. diplomat said Tuesday it was in North Korea's own interest to fulfill promises under an agreement to take initial steps to abandon its nuclear programs, amid historic talks where Pyongyang is seeking to normalize relations with its longtime foes: Japan and the United States.

U.S. Deputy Secretary of State John Negroponte noted that an early test of North Korea's willingness to disarm would occur within 60 days, the deadline for Pyongyang to shut down its sole operating nuclear reactor under a Feb. 13 agreement with the United States and four other countries.

"We should all be attentive to what North Korea does," he told a news conference in Seoul. "It's in North Korea's interest to comply with this obligation."

• Monitor the nuclear showdown on the Korean Peninsula in FOXNews.com's North Korea Center.

The agreement also calls for improved relations among regional powers, creating a series of working groups to discuss denuclearization and a peace regime to replace the 1953 cease-fire that has been in place since the end of the Korean War.

In New York, the chief nuclear envoys from the U.S. and North Korea on Monday ended the first of two scheduled days of meetings on normalizing relations but declined to make any comments.

North Korean Vice Foreign Minister Kim Kye Gwan and U.S. Assistant Secretary of State Christopher Hill were to meet again Tuesday, raising expectations for improved U.S. relations with a country President George W. Bush called part of an "axis of evil" five years ago, along with Iran and prewar Iraq.

U.S. State Department spokesman Sean McCormack sought to downplay expectations, saying this week's meetings would focus on setting the agenda for the U.S.-North Korea talks — noting the establishment of normal relations "would take some time."

"It would be a matter of building up trust. It would be a matter of performance. And today is just an initial discussion on that process," he said in Washington.

Meanwhile, Japanese and North Korean officials were to begin talks Wednesday in Vietnam to discuss improved relations under another working group created by the Feb. 13 agreement.

On Tuesday, Japan's chief envoy said North Korea's abductions of Japanese citizens and reparations for Japan's wartime aggression would top the agenda.

"There was no difference between our views that (these are) the issues that must be addressed, and we agreed on the importance to discuss them thoroughly," Japan's chief envoy Koichi Haraguchi said after a preliminary meeting with his North Korean counterpart, Song Il Ho.

North Korea admitted in 2002 that it abducted 13 Japanese citizens in the 1970s and 80s. Pyongyang sent five of them home later that year but insisted that the rest were dead, but Japan demands proof and says more of its citizens may have been taken.

The disarmament agreement has also raised hopes of renewed detente between the Koreas, whose attempts toward reconciliation since a 2000 summit between their leaders has been frustrated by the nuclear standoff.

Amid speculation of a second summit bringing together leaders of the two Koreas, the pro-government Uri Party said Tuesday that a senior aide to South Korean President Roh Moo-hyun will visit North Korea this week.

Lee Hae-chan, a former prime minister and current member of parliament, will travel to Pyongyang on Wednesday on a visit that will include a meeting with North Korea's No. 2 leader, Kim Yong Nam, said Seo Hye-seok, a spokeswoman for the pro-government Uri Party.

"The trip is aimed at discussing establishing a peace regime on the Korean peninsula with regard to implementing the Feb. 13 agreement," Seo said.

In Seoul, the U.S. diplomat Negroponte declined to say if there were any concrete plans for Americans to travel to Pyongyang, but added that such a trip would not "be surprising at all."

Negroponte said Washington believes that the series of actions outlined in the Feb. 13 agreement — including lifting trade sanctions and removing North Korea from the U.S. list of state sponsors of terrorism — could happen rapidly if North Korea moves to abandon its nuclear program.

"We would like these negotiations to move as quickly as possible and for conclusions to be reached as soon as possible," he said.

Complete coverage is available in FOXNews.com's North Korea Center.