"We have absolutely no interest and no willingness on the part of this administration to give them any economic aid at all," Clinton said.

"We are very serious about trying to make it clear to the North Koreans that their recent behaviour is absolutely unacceptable"

Hillary Clinton,
US secretary of state

"That money is in there in the event, which at this point seems implausible if not impossible, the North Koreans return to the six-party talks and begin to disable their nuclear capacity again."

On Wednesday, North Korea threatened to conduct new tests of nuclear weapons and long-range missiles.

It said the tests would take place unless the United Nations security council apologises for condemning its controversial rocket launch early last month.

North Korea said the April 5 launch placed an experimental communications satellite into orbit, but US military officials believe it was cover for a test of a long-range missile.

Following the UN condemnation, North Korea announced it was pulling out of the six-party denuclearisation talks, expelled international nuclear inspectors and declared that it would restart all its nuclear facilities.

North Korea has threatened to carry out more rocket launches and weapon tests [EPA]
Commenting on the North Korean moves, Clinton said the leadership in Pyongyang were "digging themselves into a deeper and deeper hole with the international community".

"We are very serious about trying to make it clear to the North Koreans that their recent behaviour is absolutely unacceptable."

In February 2007, North Korea agreed to end and dismantle its nuclear programmes in return for economic aid and diplomatic concessions.

But the deal faltered on disagreements over the standards by which North Korea would be judged to have fully declared all aspects of its weapons programme.

In December, the US suspended shipments of fuel aid to the North until it agreed to specific steps to verify its nuclear activities, which Pyongyang refused to do.