The United States said Monday it expects North Korea to formally agree to let inspectors take samples from weapons-grade nuclear sites during a high-level international meeting next month in Beijing.

North Korea insists it never agreed to the removal of samples, saying that outside verification of its nuclear inventory will involve only field visits, confirmation of documents and interviews with technicians.

However, US State Department spokesman Sean McCormack told reporters "it (sampling) is part of the agreement" which Washington reached with Pyongyang last month in exchange for striking North Korea from a terrorism blacklist.

"And we hope and would expect that the verification protocol would be formalized in the six-party sense at the next heads of delegations meeting," McCormack said.

US Secretary of State Condoleezza Rice said Sunday that the meeting would be held on December 8 in Beijing.

The talks will bring together Christopher Hill, assistant secretary for East Asian and Pacific Affairs, with his counterparts from the five other parties in the disarmament negotiations -- the two Koreas, China, Russia and Japan.

McCormack sidestepped the issue when asked again if there was a written document showing the removal of samples to part of the agreed steps to verify nuclear disarmament.

"Regardless of which form it may be in, it is an agreement. That doesn't change it," McCormack said.

"So what we hope is going to happen at this next six-party heads of delegation meeting is that this is agreed upon and put in a form that all the members in the six parties can validate," McCormack added.

He appeared to criticize North Korea for saying it would suspend a historic cross-border railway service starting next week and restrict other frontier crossings in protest at what it called South Korea's policy of confrontation.

The hardline communist state also said it would "selectively expel" South Koreans based at two joint projects developed as symbols of reconciliation, the Kaesong industrial estate and the Mount Kumgang tourist resort.

"We've always encouraged direct discussions and direct interaction between the North and South. The North can only benefit from greater contact with the rest of the world, including South Korea," McCormack said.