Lt. Col. James Holley, from Kansas, stands at the Combined Battle Simulation Center for the annual joint military exercises between the United States and South Korea, at a U.S. military base in Seoul, South Korea, Thursday, March 11, 2010. About 18,000 American soldiers and an undisclosed number of South Korean troops are taking part in the drills, dubbed "Key Resolve" and "Foal Eagle," according to U.S. and South Korean military officials. (AP Photo/Lee Jin-man, Pool) (Lee Jin-man - AP)

 

 

Gen. Walter Sharp, commander of the U.S. Forces Korea, answers a reporter's question during a press conference on the annual joint military exercises between the United States and South Korea, at a U.S. military base in Seoul, South Korea, Thursday, March 11, 2010. About 18,000 American soldiers and an undisclosed number of South Korean troops are taking part in the drills, dubbed "Key Resolve" and "Foal Eagle," according to U.S. and South Korean military officials. (AP Photo/Lee Jin-man, Pool) (Lee Jin-man - AP)

 

Gen. Walter Sharp, commander of the U.S. Forces Korea, answers a reporter's question during a press conference on the annual joint military exercises between the United States and South Korea, at a U.S. military base in Seoul, South Korea, Thursday, March 11, 2010. About 18,000 American soldiers and an undisclosed number of South Korean troops are taking part in the drills, dubbed "Key Resolve" and "Foal Eagle," according to U.S. and South Korean military officials. (AP Photo/Lee Jin-man, Pool) (Lee Jin-man - AP)

 

 

A U.S. Marine, left, interacts with South Korean marines in an anti-terrorism defense drill for the joint U.S.-South Korean military exercises Key Resolve/Foal Eagle 2010 at Commander, Fleet Activities, Naval Base, in Chinhae, South Korea, Thursday, March 11, 2010. (AP Photo/Ahn Young-joon) (Ahn Young-joon - AP)

 

 

South Korean marines aim their weapons after they arrested a mocked terrorist in an anti-terrorism defense drill for the joint U.S.-South Korean military exercises Key Resolve/Foal Eagle 2010 at Commander, Fleet Activities, Naval Base, in Chinhae, South Korea, Thursday, March 11, 2010. (AP Photo/Ahn Young-joon) (Ahn Young-joon - AP)

 

 

Mock terrorists run during an anti-terrorism defense drill for the joint U.S.-South Korean military exercises Key Resolve/Foal Eagle 2010 at Commander, Fleet Activities, Naval Base, in Chinhae, South Korea, Thursday, March 11, 2010. (AP Photo/Ahn Young-joon) (Ahn Young-joon - AP)

 

 

A U.S. Marine, left, interacts with South Korean Marines during an anti-terrorism defense drill, as part of the joint U.S.-South Korean military exercises Key Resolve/Foal Eagle 2010 at Commander, Fleet Activities, Naval Base, in Chinhae, South Korea, Thursday, March 11, 2010. (AP Photo/Ahn Young-joon) (Ahn Young-joon - AP)

 

 

A U.S. Marine, second from left, interacts with South Korean Marines during an anti-terrorism defense drill, as part of the joint U.S.-South Korean military exercises Key Resolve/Foal Eagle 2010 at Commander, Fleet Activities, Naval Base, in Chinhae, South Korea, Thursday, March 11, 2010. (AP Photo/Ahn Young-joon) (Ahn Young-joon - AP)

 

U.S. Marines participate in an anti-terrorism defense drill during the joint U.S.-South Korean military exercises Key Resolve/Foal Eagle 2010 at Commander, Fleet Activities, Naval Base, in Chinhae, South Korea, Thursday, March 11, 2010. (AP Photo/Ahn Young-joon) (Ahn Young-joon - AP)

"They are here for this exercise and if we ever went to war, they would naturally come also," Army Gen. Walter Sharp told reporters at Yongsan Garrison, the main U.S. military headquarters in central Seoul.

Sharp said that the troops are carrying out daily exercises with South Korean troops to practice locating, securing and eliminating the North's weapons of mass destruction.

The North, believed to have enough weaponized plutonium for at least a half-dozen bombs, quit international disarmament-for-aid negotiations and conducted a second nuclear test last year, drawing tightened U.N. sanctions.

Pyongyang also has been developing a long-range missile designed to strike the U.S., and has stockpiled between 2,500 and 5,000 tons of chemical agents and is believed to be capable of producing biological weapons, according to South Korea's Defense Ministry.

"What we are training for is all the threats that North Korea can throw at us," Sharp said.

Sharp's comments came as the North has been escalating its rhetoric against the U.S. and South Korea over their annual military drills that began Monday.

About 18,000 American soldiers and an undisclosed number of South Korean troops are taking part in the war games, dubbed Key Resolve and Foal Eagle, according to U.S. and South Korean militaries. Some involve computer simulation.

Pyongyang, which says they are a rehearsal for attack, warns it will bolster its nuclear capability and put its troops on high alert in response to the drills.

The U.S. says they are purely defensive and that it has no intention of invading the North.

"We have done these exercises before," State Department spokesman P.J. Crowley told reporters Wednesday. "These should not be a surprise to North Korea."

Sharp said the 28,500 U.S. troops stationed in the South are prepared to deal with any contingency in North Korea, but called for a diplomatic solution to end North Korea's nuclear programs and urged Pyongyang to rejoin stalled six-nation talks.

"North Korea's development of nuclear weapons is seriously undermining international non-nuclear proliferation regimes as well as posing a threat" to the region, Prime Minister Chung Un-chan told a Seoul forum.

The North has demanded a lifting of the sanctions and peace talks with the U.S. on formally ending the 1950-53 Korean War before it returns to the talks.

The U.S. and South Korea have responded that the North must first return to the negotiating table and make progress on denuclearization. The talks involve China, Japan, the two Koreas, Russia and the United States.

Separately, former U.S. Secretary of State Henry Kissinger said at a lecture in Seoul that he supports sanctions not for the purpose of causing what he called "chaos," but rather to provide the country "a way out, into negotiations."

Former U.N. nuclear chief Mohamed ElBaradei, however, told a forum earlier in the day that he believes sanctions will not work and called on the U.S. to engage North Korea and assure it regarding security.

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Associated Press writers Hyung-jin Kim, Sangwon Yoon and Nate Kim and AP Television News cameraman Yong-ho Kim contributed to this report.