SEOUL: South Korea and Japan stepped up pressure Thursday on North Korea to quickly rejoin nuclear disarmament talks, while a senior U.N. envoy was in Pyongyang amid a flurry of diplomacy to reopen the on-and-off negotiations.

In Beijing, top nuclear negotiators were to meet Thursday for a third straight day to discuss how to jump-start the six-nation talks that involve the two Koreas, the U.S., China, Russia and Japan.

The past two days of talks in Beijing were believed to focus on North's calls for the lifting of U.N. sanctions and a peace treaty with Washington formally ending the 1950-53 Korean War as preconditions for its return to the disarmament talks, South Korea's Yonhap news agency said in a report citing unidentified diplomatic sources.

In Seoul, the foreign ministers of South Korea and Japan brushed aside North Korea's demand, saying the regime first must return to the disarmament talks and show progress on denuclearization before any discussion on a peace treaty or sanctions.

"We shared the view that North Korea's return to the six-party talks and substantial progress in its denuclearization must be made first," South Korean Foreign Minister Yu Myung-hwan told reporters during a joint press conference with his Japanese counterpart, Katsuya Okada.

Okada also said he and Yu agreed North Korea must first carry out denuclearization and other measures.

South Korea and Japan will maintain a "two-track" policy of implementing sanctions while engaging in dialogue, Yu said.

Washington also has said Pyongyang must return to the talks first before any discussion about political and economic concessions.

North Korea walked away from the negotiations last year during a standoff over its nuclear and missile programs but has been reaching out to Washington, Seoul and Beijing in recent months.

Analysts say the about-face shows the regime is feeling the pinch from sanctions and may agree to return to the talks in exchange for aid. Impoverished North Korea relies on outside handouts to feed its 24 million people, and the food shortage is expected to be worse this year, the state-run Korea Rural Economic Institute in Seoul said Wednesday.

In Pyongyang, the U.N.'s political chief, B. Lynn Pascoe, met Wednesday with North Korean Foreign Minister Pak Ui Chun, according to broadcaster APTN in North Korea. His visit is the first by a high-level U.N. official since 2004.

The rush of diplomacy raised hopes of a breakthrough on restarting the six-party talks. North Korean leader Kim Jong Il told a high-level envoy from Beijing on Monday that Pyongyang is committed a nuclear-free Korean peninsula.