North Korea has warned that it will start a programme to enrich uranium and launch military action if the US and its allies try to isolate the country.
KCNA quoted a foreign ministry spokesman as saying that the North will use all the plutonium it extracted for weapons.
The comments followed UN sanctions imposed on Pyongyang for a nuclear test.
The sanctions resolution approved yesterday banned all weapons exports from North Korea and most arms imports into the state
It authorised UN member states to inspect North Korean sea, air and land cargo, requiring them to seize and destroy any goods transported in violation of the sanctions.
North Korea has raised tension in the region in the past months by test-firing missiles, restarting a plant to produce arms-grade plutonium and holding the 25 May nuclear test, which put it closer to having a working nuclear bomb.
The isolated country's $2bn annual trade with neighbouring China, equal to about 10% of the North's annual GDP, is its most important economic relationship.
Beijing has wanted to avoid any measures that could cause the North's economy to collapse and lead to chaos on its border.
South Korea's defence minister said this week the North's sabre rattling is to build internal support for leader Kim Jong-il, 67, as he prepares for succession in Asia's only communist dynasty.
Since Mr Kim took over in 1994 and launched his guiding ‘military first’ policy, the North's economy has grown weaker and an estimated one million people died in a famine in the late 1990s.
The new UN measures expand previous provisions to hit North Korea's arms trade, which is a key source of foreign currency for the destitute state that produces few other goods it can sell to the outside world.
A study by the US-based Institute for Foreign Policy Analysis think tank this year estimated Pyongyang earns around $1.5bn a year from missile sales.
