SYDNEY, Australia, Sept. 7 — At the invitation of North Korea, an international delegation of nuclear experts from Russia, China and the United States will travel to the North next week to inspect nuclear sites that are to be shut down, the chief American envoy to the country said here on Friday.

The announcement, by Assistant Secretary of State Christopher R. Hill, came on a day when the North’s nuclear ambitions dominated the sidelines of the Asia-Pacific Economic Cooperation forum here, creating an awkward and testy exchange between President Bush and President Roh Moo-hyun of South Korea over what would seem like a historical anachronism, the lack of a peace treaty ending the Korean War.

With Mr. Roh scheduled to go to Pyongyang to meet his North Korean counterpart, Kim Jong-il, next month, the South Korean leader used his photo opportunity with the president to make a public issue of the peace accord. With television cameras rolling, and Mr. Bush by his side, Mr. Roh publicly pressed the American president to declare a formal end to the hostilities — something Mr. Bush has said he will not do until the North has completely scrapped its nuclear program.

“I said it’s up to Kim Jong-il,” Mr. Bush said, looking irked, “as to whether or not we’re able to sign a peace treaty to end the Korean War. He’s got to get rid of his weapons in a verifiable fashion. And we’re making progress toward that goal. It’s up to him.”