SEOUL, South Korea — North Korea is ready to start dismantling its nuclear programs following the shutdown its sole operating reactor, a North Korean diplomat said Sunday, as long as America lifts all sanctions against the communist nation.

A minister at the North’s mission to the United Nations in New York, Kim Myong Gil, confirmed the reactor was shut down Saturday after receipt of a South Korean oil shipment, and said U.N. inspectors would verify the closure Sunday.

“Immediately after the arrival of the first heavy fuel oil, the facilities were shut down and the (International Atomic Energy Agency) personnel will verify that,” Mr. Kim told The Associated Press by telephone.

North Korea’s Foreign Ministry said any future progress in disarmament would depend “on what practical measures the U.S. and Japan, in particular, will take to roll back their hostile policies toward” North Korea, according to the statement carried by the official Korean Central News Agency.

IAEA inspectors were expelled from the North in late 2002 at the start of the nuclear crisis. A 10-member team arrived Saturday in North Korea to make sure the reactor at Yongbyon was switched off — the first step by the North to scale back its weapons program since the standoff began.

Mr. Kim noted that the next steps included the North making a declaration of its nuclear program and disabling the facilities.

But he said that would happen only if Washington takes actions “in parallel,” including removing wider economic sanctions and striking the country from a list of states that sponsor terrorism.

“After the shutdown, then we will discuss about the economic sanctions lifting and removing of the terrorism list. All those things should be discussed and resolved,” Mr. Kim said.

The main American envoy on the North Korea nuclear issue, Assistant Secretary of State Christopher Hill, has said he believes the North’s nuclear facilities could be completely disabled by the end of the year and that he expected a complete declaration of its atomic programs within months.

Responding to the North’s demand that sanctions be lifted, Mr. Hill said Sunday in Seoul: “They want some things, we want some things, and we have to sit down and figure out how everything’s going to be sequenced.”

Japan said it was ready to discuss outstanding issues with North Korea, but said the country had already delayed implementing an agreement reached at the arms talks in February.

“The North is already running late on the agreement, and we urge them to carry through with the steps immediately,” assistant press secretary for Japan’s Foreign Ministry, Nori Shikata, said.

Mr. Hill said earlier in Tokyo that it could take the IAEA at least a day to verify the shutdown because there were five sites within the North’s nuclear complex to inspect, including the reactor.

Despite the lack of verification, the American diplomat said he was confident the shutdown had begun.

“I think we have every reason to believe they have started the shutdown,” he said, adding that the complete process would take a few days to allow equipment to cool before IAEA seals could be applied.

Mr. Hill was touring the region ahead of resumed six-nation nuclear talks with North Korea starting Wednesday in Beijing. That session will focus on setting up a “work plan and a timeframe” for how disarmament would proceed, Mr. Hill said in Seoul, adding he planned to meet his North Korean counterpart Tuesday ahead of the formal start of talks.

Mr. Hill also said he hoped working groups set up under the talks process — to discuss details of the North’s disarmament and on normalizing its relations with America and Japan — could resume meeting by the end of August.

“If we don’t take these steps a little more quickly than we’ve taken that first step, then we’re going to fall way behind again,” Mr. Hill said.

South Korea’s nuclear envoy Chun Yung-woo called the North’s shutdown a “milestone” and told the AP the resumed nuclear negotiations would be held “in a better atmosphere than ever before.” The talks last met in March.

Still, Mr. Chun stressed “the next phase will be more difficult than the reactor shutdown.”

The oil that the North received Saturday via a South Korean ship was an initial 6,200 tons of a total 50,000 tons as a reward for the reactor shutdown. Under a February agreement at the arms talks, North Korea will receive a total equivalent of 1 million tons of oil for dismantling its nuclear programs.

North Korea withdrew from the Nuclear Nonproliferation Treaty and restarted its reactor in early 2003, after Washington accused it of a secret uranium enrichment program in violation of an earlier disarmament deal and halted oil deliveries.

International negotiations on the issue have snagged on a variety of issues, including the North’s anger over comments by American officials about its government and financial restrictions placed on a bank where North Korea held accounts.

Moves to resolve the standoff gained momentum in the wake of North Korea’s underground test nuclear explosion in October, after which America took steps to reverse its previous hard-line policy and accommodate North Korean demands.