The chief U.S. nuclear envoy expressed optimism after a day of meetings with his North Korean counterpart Tuesday, saying no new obstacles emerged to progress on disarmament following Pyongyang's shutdown of its sole operating reactor.

The U.S. representative at six-party talks on North Korea's nuclear disarmament said Friday he hoped the country would disable its Yongbyon nuclear reactor by the end of 2007.

The North Korean government has issued a positive assessment of a senior U.S. envoy's visit to the capital, Pyongyang. United Nations nuclear inspectors are expected to arrive in North Korea on Tuesday to plan for the imminent shutdown of the North's main nuclear reactor, a crucial first step toward the goal of Pyongyang' full nuclear disarmament.

U.S. chief nuclear negotiator Christopher Hill says he had "good talks" with North Korean officials in Pyongyang and believes they are prepared to promptly shut down the country's Yongbyon nuclear reactor.

The main U.S. nuclear envoy said Tuesday that the pending release of North Korea's money frozen at a Macau bank should pave the way for Pyongyang to meet its obligations under a disarmament agreement.

The top U.S. nuclear envoy said Monday that a mid-April deadline for North Korea to shut down its nuclear reactor is becoming difficult to meet because of an ongoing dispute over frozen North Korean funds.