Officials did not disclose the “practical measures”, but a spokesman for the communist state’s foreign ministry said if the United States tried to force North Korea to give up its nuclear weapons programme without a non-aggression treaty, it would lead to war.

North Korea has threatened to strengthen its nuclear weapons programme as a "deterrent" against what it calls a US plan to invade.

"The DPRK (Democratic People's Republic of Korea ) is taking practical measures to steadily beef up the nuclear deterrent force as a just self-defensive means to repel the US nuclear pre-emptive attack and ensure peace and security on the Korean Peninsula," the North Korean spokesman said.

Trading demands

"It was confirmed that the US does not wish to co-exist with the DPRK in peace but tries to use the six-way talks as a leverage to completely disarm the latter," he said. "This compels the DPRK to discard any interests or expectation for the talks."

The talks stalled over Washington’s demands that North Korea should first dismantle its nuclear programmes.

North says it will do so only if the United States signs a non-aggression treaty, provides economic aid and opens diplomatic ties.

The North Korean crisis erupted last October when the United States said Pyongyang had admitted to working on developing enriched uranium for weapons.