North Korea has warned it will hit back at the US if it is attacked as tensions grow over a possible crackdown on exports of suspected weapons parts from the North.

In a commentary on Monday, North Korea's Rodong Sinmun newspaper, declared that North Korea was a "proud nuclear power", and said the US should "take a correct look at whom it is dealing with".

"It would be a grave mistake for the US to think it can remain unhurt if it ignites the fuse of war on the Korean peninsula," the paper said.

The commentary came as the US navy continued to track a North Korean cargo ship off the coast China believed to be carrying missiles and missile parts. 

The 2,000-ton freighter Kang Nam left North Korea last Wednesday and is reportedly on its way to Myanmar.

Pentagon officials say they suspect the ship is carrying prohibited materials.

The sanctions firm up an earlier arms embargo and authorise ship searches in an attempt to thwart North Korea's nuclear and ballistic missile programmes.

North Korea has said it would view any such searches as an act of war.

Missile test

With tensions high, Barack Obama, the US president, has said he is ready to cope with "any contingencies" involving North Korea amid reports that North Korea may be preparing for another long range missile test.

Japanese media reports have said the test may be timed to coincide with US independence day on July 4.

Speaking to the US TV network CBS, Obama said the US was prepared for any North Korean provocation, including the possibility of a North Korean missile test toward Hawaii.

Robert Gates, the US defence secretary, has ordered additional protections for Hawaii as a precaution.

"This administration - and our military - is fully prepared for any contingencies," Obama told CBS, in an interview due to be broadcast on Monday.

"I don't want to speculate on hypotheticals," Obama said. "But I want… to give assurances to the American people that the t's are crossed and the i's are dotted in terms of what might happen."