Seoul, South Korea ? North Korea indicated it was ready to promptly shut down a plutonium-producing reactor, a U.S. envoy said Friday, the latest sign the communist country may live up to its pledge to stop making nuclear weapons.

Still, Assistant Secretary of States Christopher Hill, returning from a surprise two-day trip to North Korea, cautioned that completely disarming the communist country would be a long and arduous process.

Hill said he was “buoyed by a sense that we are going to be able to achieve our full objectives, that is complete denuclearization, but also burdened by the realization of the fact that we’re going to have to spend a great deal of time, a great deal of effort, a lot of work in achieving these.”

Hill met with North Korea’s chief nuclear negotiator and foreign minister during the first trip by a high-ranking U.S. official to the country since October 2002.

Last week, the secretive state invited inspectors from the International Atomic Energy Agency to begin discussions on the procedures for shutting down its Yongbyon reactor. The country expelled the U.N. nuclear inspectors in late 2002.

North Korea “indicated that they are prepared promptly to shut down the Yongbyon facility as called for in the February agreement,” Hill said.

The February pact between North Korea and five other nations called for North Korea to close the reactor by mid-April and allow in U.N. inspectors in exchange for energy aid.

But North Korea missed the deadline over a delay in resolving a separate financial dispute involving the country’s funds frozen at a Macau bank.

The bank was blacklisted by the U.S. for allegedly aiding North Korea in money laundering and counterfeiting. The $25 million was freed earlier this year with U.S. blessing, but it was only last week that it began to be transferred to a North Korean account at a Russian bank.