The United States has announced that an American delegation will travel to North Korea next month , in an attempt to gain access to an underground site that Washington suspects may be part of Pyongyang's nuclear programme.

A State Department spokesman said the delegation would not be satisfied with verbal assurances and would demand to see the complex to clarify its use.

Washington has long sought to inspect North Korea's underground facilities to check whether it is complying with a freeze on developing nuclear weapons, agreed in 1994.

There's been no word from North Korea on how it will respond to the American demand.