PYONGYANG -?The Democratic People's Republic of Korea (DPRK) accused the United States and the Republic of the Korea (ROK) of plotting to bring down its socialist system, the official KCNA news agency reported Thursday.

This clearly proves that the United States and the ROK lacked the sincerity to improve their relationship with the DPRK, but instead sought to "bring down its system" and start a war, the spokesman said.

The People's Army and the people of the DPRK have a firm, unshakable faith, he added.

He stressed that the DPRK will bolster up its "nuclear deterrent" for self-defense capable of warding off any attack, and keep its arms ready for action all the times.

"Those who seek to bring down the system in the DPRK ... will fall victim to the unprecedented nuclear strikes of the invincible army and the just war to be waged by all the infuriated service personnel and people," he said.

The?ROK newspaper Dong-A Ilbo reported that several institutes of?the ROK?would hold a conference presided over by the United States in mid-April to discuss the possibility of "contingency" in the DPRK and?a "proposal for cooperation".