North Korea stepped up criticism of ongoing U.S.-South Korea military exercises, warning Wednesday that it would boost its "war deterrent" _ a euphemism for its nuclear programs.

North Korea "will increase its war deterrent in every way as long as the U.S. and its followers continue posing military threats to it," a spokesman for the North's Foreign Ministry said in comments carried by the country's official Korean Central News Agency.

The remarks came two days after South Korea and the U.S. launched Ulchi Freedom Guardian, an annual computer-simulated war game and follow daily criticisms of the exercises in North Korean media.

The exercises come amid a dispute between the U.S. and North Korea over ways to verify the North's declared nuclear programs under an aid-for disarmament deal.

North Korea often uses "deterrent," "war deterrent," or "nuclear deterrent" to refer to its nuclear programs. The country carried out an underground nuclear test blast in 2006.

The drill, which runs through Thursday, involves 56,000 South Korean troops and 10,000 U.S. soldiers in South Korea and abroad, and is aimed this year at preparing Seoul to retake wartime command of its forces from Washington in 2012.

North Korea regularly calls the drills a prelude to attack. Seoul and Washington have dismissed the North's accusations, describing the war games as purely defensive.

The Foreign Ministry spokesman Wednesday accused the U.S. and South Korea of planning a "pre-emptive nuclear attack."

On Monday, the North blamed the U.S. for delaying its removal from a U.S. terror blacklist. The U.S. has said it will delist North Korea from the list only after Pyongyang has agreed to a full nuclear verification plan.

The North's spokesman accused the U.S. for making "unjust demands" regarding the verification issue.

Separately, South Korea's top negotiator at the nuclear talks called for patience in putting in place the verification regime and asked for China to play a constructive role to help spur the process.

"It is likely to take more time as differences remain between the U.S. and North Korea," Kim Sook told reporters, according to the Foreign Ministry.

China since 2003 has served as host for the six-party talks on North Korea that also include Japan, Russia, South Korea and the U.S.

The U.S.-South Korea military drills also came amid lingering tensions on the Korean peninsula over the shooting death last month of a South Korean tourist at a North Korean mountain resort.

The North has said the tourist was shot because she entered a restricted military area and ignored warnings to stop. In response, Seoul suspended tours to the resort and demanded the North allow investigators into the area. North Korea has refused.