BEIJING — North Korea told delegates at nuclear talks on Saturday that it is preparing to shut down its main reactor, South Korea’s chief nuclear envoy said, a key step promised in a landmark disarmament pact.

The apparent progress in implementing last month’s agreement came only hours after North Korea’s lead nuclear envoy said his government would not close its main nuclear facility until all $25 million of its money frozen in a Macau bank is released.

But U.S. Assistant Secretary of States Christopher Hill, the top American envoy, said late Saturday that the North was still “fulfilling their obligations.”

The fate of the frozen funds, the result of a blacklisting by U.S. authorities, has become a central issue in the talks. The U.S. promised to resolve the bank issue as an inducement to North Korea to return to the negotiations, but its solution — an order this past week to U.S. banks to sever ties with Banco Delta Asia — has been criticized by China and left North Korea sending mixed signals.

At one follow-up meeting Saturday, another North Korean diplomat, Kim Song Gi, said North Korea has “begun preparations to shut down its Yongbyon nuclear facility,” South Korean envoy Chun Yung-woo told reporters afterward.

Kim promised that North Korea will submit a list of its nuclear programs and disable its nuclear facility “as soon as the right conditions are created,” Chun said, without explaining what the conditions were.

Chun did not independently confirm whether shutdown preparations were under way.

Under the Feb. 13 agreement, which involves the United States, China, Japan and Russia as well as the two Koreas, North Korea has 60 days to shutter the Yongbyon reactor and a plutonium processing plant which have produced material for a nuclear weapons program.

U.N. monitors are supposed to be allowed in North Korea to verify the shutdown, and once confirmed North Korea is to receive energy and economic assistance.

The United States, in a side agreement, promised to resolve the Banco Delta Asia funds, which U.S. authorities alleged may have resulted from counterfeiting or money laundering.

“We are on schedule for this first phase,” Hill told reporters after daylong meetings with delegates in the other five countries.