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Analysts see North Korea's threats as bargaining chips to try to persuade the US and its regional allies to lift trade barriers and increase aid.

But Washington has shown no signs of changing its hard-line policy on the state, which Mr Bush has included in an "axis of evil".

Pyongyang said on Friday that the stopping of the ship "wantonly violated the routine trade between countries", and accused the US of "high-handed piracy".

Following the interception, North Korea warned that it would unfreeze work at a nuclear plant in Yongbyon.

North Korea said it needed the nuclear power to make up for the electricity shortfall caused by the ending of heavy fuel oil shipments, which Washington and its allies halted after Pyongyang allegedly admitted to an another nuclear programme in October.

No war talk

White House spokesman Ari Fleischer described the threat to reactivate the plant as "regrettable" but said it would not force Washington into dialogue with Pyongyang.

But neither is there talk of military action from the White House.

President Bush has denied that the US is guilty of double standards in using diplomatic pressure to isolate North Korea, while warning of war against Iraq.

"Not every issue requires a potential military response," he said, in an interview with ABC News to be broadcast on Friday.

The BBC's Matt Frei in Washington says that war is not an option with North Korea, which has a million men under arms and is in striking range of the 37,000 US forces massed in the South.

Meanwhile Japan described the threat as "deplorable", but nevertheless said it would try to restart talks with North Korea.

Taechon: 200-MWe nuclear power reactor - construction halted under Agreed Framework

Pyongyang: Laboratory-scale "hot cells" that may have been used to extract small quantities of plutonium

Kumho: Site of two 1,000-MWe light water reactors under construction by Kedo