By Jon Herskovitz
SEOUL (Reuters) - A senior U.S. envoy extended talks in North Korea on Thursday in a bid to save a troubled disarmament pact and convince secretive Pyongyang not to restart its nuclear plant.
The visit to the isolated North by U.S. Assistant Secretary of State Christopher Hill came as the rival Korean states held their first discussions in almost a year, but with no discernible progress.
The flurry of diplomacy coincided with a report that North Korea might be about to ratchet up regional tensions by upgrading a launch site used to test missiles that can hit all of South Korea and most of Japan.
Hill, who went to Pyongyang on Wednesday, was scheduled to hold a second day of talks with the North's top nuclear envoy on Thursday, the State Department said.
Hill had been expected to drive back to Seoul on Thursday but South Korea's Foreign Ministry said Hill would now stay in Pyongyang at least until Friday.
Local media reported that Hill was ready to offer a compromise on how to check statements by the North about its nuclear programme in an effort to revive a faltering disarmament-for-aid deal agreed with regional powers.
But State Department spokesman Sean McCormack said on Wednesday that Hill was not going to Pyongyang with an offer to change the "substance" of any verification mechanism.
The North baulked at U.S. verification demands, fearing that they would be too intrusive. Washington countered by saying it would only remove Pyongyang from its terrorism blacklist once the North had agreed to a "robust" verification system.
The North started to disable Yongbyon in November under the deal it reached with China, Japan, Russia, South Korea and the United States. In recent weeks it threatened to restart the plant in anger at remaining on the U.S. terrorism list.
LOOKS TO BUSH SUCCESSOR?
Analysts have said North Korea might be trying to pressure the outgoing Bush administration as it seeks diplomatic successes to bolster its legacy. The North might also think it could reach a better deal under a new U.S. president.
The International Atomic Energy Agency said last week that North Korea had expelled monitors from the plutonium-producing part of its Yongbyon nuclear plant and planned to start reactivating the Soviet-era reactor in a week's time. IAEA monitors remained in other areas of the complex, it said.
North and South Korea held their first discussions on Thursday since Pyongyang cut off inter-Korean dialogue early this year in anger at the policies of the South's conservative new president, who wanted to tie aid to disarmament.
Analysts saw the North's proposal for working-level military talks as a possible olive branch heralding future discussions. But Thursday's session ended shortly after it began with both sides airing a list of grievances and then adjourning.
North Korea has also been upgrading facilities at the site of its past missile tests in what might be preparations for another long-range missile launch, a Seoul daily reported.
(Additional reporting by Jack Kim; editing by Roger Crabb)
