The US has issued a stark warning to North Korea that it must allow inspections of its suspected nuclear weapons programme or risk delaying a major power deal.

It is now time for us to see the same kind of tangible progress by (North Korea) in meeting its commitments

Jack Pritchard, US delegate to Kedo

Jack Pritchard, the most senior Washington official to visit North Korea since 2000, was speaking at a ceremony to mark the start of construction of two light-water nuclear reactors for the North.

They are being built as a result of a 1994 agreement under which North Korea suspended its suspected nuclear weapons programme, averting a potential nuclear crisis on the Korean peninsula.

Under the deal, North Korea undertook to allow UN inspections of suspected nuclear sites before key components for the reactors could be delivered, but it has repeatedly stone-walled.

Time to co-operate

"It is now time for us to see the same kind of tangible progress by (North Korea) in meeting its commitments," said Mr Pritchard, US delegate to Kedo - the international organisation responsible for building the plant.

1994 Agreed Framework

West to supply fuel oil and build 2 nuclear reactors N Korea to freeze suspected nuclear weapons programme N Korea still has to allow in UN weapons inspectors US fears N Korea had extracted plutonium for 2 nuclear bombs before 1994

The UN agency IAEA (International Atomic Energy Agency) estimates that it will take at least three years to complete inspections. If North Korea does not allow them soon, that will put back the 2005 scheduled completion.

Mr Pritchard said: "(North Korea) must start meaningful cooperation now with the IAEA and must comply with all of its obligations under the Agreed Framework".

The $4.6bn project is being constructed at the village of Kumho on North Korea's eastern coast.

The 1,000-megawatt light-water reactors will produce less weapons-grade material than the North's mothballed graphite nuclear reactors.

Milestone

Around 150 representatives from Kedo and journalists travelled to the North for the ceremony.

Fireworks lit up the sky around the building site and a hopper of wet cement was ceremoniously lowered into the reactors' foundations.

Kedo executive director Charles Kartman said the project was not simply about building nuclear reactors.

"This project is about preserving peace and stability on the Korean peninsula," he said.

The ceremony marks a milestone in a project which has been dogged by delays, including rows over wages for North Korean workers and it is already well behind its original target date of 2003.

Some analysts in the US remain sceptical about the project and have called for it to be scrapped or halted until Pyongyang allows in inspectors.

Nevertheless, the ceremony comes as the reclusive North has shown fresh signs of wanting to re-engage with the outside world including holding high-level talks with the United States and Japan.