U.S. Assistant Secretary of State Christopher Hill has been mostly silent on the details of his three days of talks in Pyongyang. He said the focus of the discussions was finding a way to verify claims the North made about its nuclear program.
"Reports on North Korea having made a very important suggestion or issued an ultimatum seem to be grounded on matters in the past. It is different from what was discussed at Hill's recent visit, which was a verification protocol," Foreign Minister Yu Myung-hwan told a parliamentary committee.
A pro-Pyongyang newspaper said on Monday that North Korea "seems to have delivered its opinion on peacefully resolving the nuclear issues ... and issued an ultimatum in relation to this".
The Choson Sinbo newspaper, published in Japan, did not elaborate on the ultimatum but said if there was no agreement, North Korea would likely step away from disarmament talks.
Yu said the North would try to evade verification as much as it can. "What we need to do is to make it impossible for (the North) to run away."
Analysts have speculated Hill may have reached some kind of deal or understanding in Pyongyang that is delicate in nature and requires the support of the other parties in the nuclear talks -- China, Japan, Russia and South Korea.
Yu would not offer any details of Hill's talks but said he thought both sides were showing flexibility.
South Korea's Yonhap news agency quoted a government source as saying North Korea asked for additional compensation to accept the sweeping verification demanded by Washington.
The nuclear agreement North Korea struck with the five regional powers in February 2007 seemed in peril after Pyongyang, angry at not being removed from a U.S. terrorism blacklist, vowed last month to rebuild the ageing Yongbyon nuclear plant, its source for weapons-grade plutonium.
Washington said it would take the North off the terrorism list, bringing economic and diplomatic benefits, once a system had been agreed to verify its nuclear claims.
In late September, Pyongyang ordered the expulsion of U.N. monitors from Yongbyon and said it planned to start reactivating the Soviet-era plant within days.
Disablement started last November and was aimed at taking at least a year to reverse.
The U.S. State Department said that despite Hill's visit, the North continued to make moves to restart Yongbyon.