Pyongyang, Mar 29 (IANS): North Korean leader Kim Jong Un has ratified a strike plan by the Strategic Rocket Force as US B-2 stealth bombers flew over the Korean Peninsula, the KCNA news agency reported Friday.

"The time has come to settle accounts with the US imperialists in view of the prevailing situation," Xinhua quoted Kim Jong Un as saying after an urgent meeting with top military officials early Friday.

He ratified a plan of the Strategic Rocket Force for firepower strike on the US and South Korea if they "make a reckless provocation", said the KCNA.

Kim said the latest US move is "not a simple demonstration of forces" but "an ultimatum that will ignite a nuclear war at any cost on the Korean Peninsula".

Two B-2 Spirit bombers were sent to the Korean Peninsula Thursday for a firing drill but US Defense Secretary Chuck Hagel denied that flying the bombers to the peninsula would aggravate the situation in the region.

Tensions have been running high on the Korean Peninsula since North Korea conducted its third nuclear test Feb 12 as a countermeasure against the joint military drills of the US and South Korea.

North Korea also threatened to launch a pre-emptive nuclear strike for self-defense and unilaterally nullified the 1953 armistice that suspended the Korean War.