TOP US nuclear negotiator Christopher Hill was on Friday afternoon to begin a second day of talks with his North Korean counterpart in Singapore after an unexplained delay in the meeting.

Mr Hill left his hotel in the early afternoon and gave no explanation as to why the meeting had not begun in the morning as planned.

'I don't know,' he told reporters before getting into a chauffeured car waiting at his hotel.

A US embassy spokesman said earlier that Mr Hill had gone to the embassy, where the talks are held, ahead of the originally scheduled meeting, due to begin at 10am (Singapore time).

But witnesses outside the North Korean embassy residence, where the visiting North Korean nuclear envoy Kim Kye Gwan stays, said his car did not leave the building in the morning.

Asked why, an embassy staff member said 'I have no idea,' before telling AFP not to call again and hanging up the phone.

Mr Hill and Mr Kim are in Singapore ahead of a wider meeting next week that aims to break a deadlock on verifying Pyongyang's nuclear disarmament.

Verification was among the issues discussed during the first day of consultations in Singapore on Thursday between the US and North Korean envoys, Mr Hill told reporters after that meeting.

'We are having this kind of consultation in order to make sure everyone understands what we need to get accomplished with the six-party process' expected to resume on Monday, Mr Hill said.

The six-party talks group the two Koreas, the United States, China, Russia and Japan.

The United States and North Korea differ on what was agreed when Mr Hill made a trip to Pyongyang from Oct 1-3 to try to save a shaky February 2007 disarmament deal.

After reaching an apparent agreement on verification procedures, the US announced it would drop the communist North from a terrorism blacklist, and the North reversed plans to restart its plutonium-producing nuclear plants.

However, North Korea, which tested an atomic weapon in October 2006, insists it never agreed to samples of atomic material being taken away.

It says the outside verification of its nuclear inventory, submitted in June, will involve only field visits, confirmation of documents and interviews with technicians. -- AFP