North Korea said on Friday annual war games staged by the United States and South Korea were undermining six-party nuclear talks and forcing it to raise the "quality and quantity" of its own military deterrent. The comments, from a North Korean Foreign Ministry spokesman, came as negotiations between the two Koreas, the United States, Japan, China and Russia on dismantling Pyongyang's nuclear programmes remain in limbo. The computer-simulated drills, called Ulchi Focus Lens, are designed to test U.S. and South Korean readiness for military emergencies on the Korean peninsula. They will run for 12 days from Aug. 23. "Now that the U.S. scenario for a war of aggression against the DPRK has entered the phase of its implementation, the DPRK is left with no option but to increase its war deterrent force both in quality and quantity," the spokesman said in a statement carried by the North's official KCNA news agency. DPRK is short for the North's official name, the Democratic People's Republic of Korea. "The U.S. evermore undisguised moves for war are little short of destroying the basic foundation for the six-party talks to seek a negotiated solution to the nuclear issue on the Korean peninsula," the statement said. Senior officials from the six countries have held three rounds of negotiations aimed at dismantling the North's nuclear programmes. Pyongyang is believed to be pursuing a secret uranium-based nuclear weapons programme and to have resumed a plutonium-based plan it had previously agreed to freeze.