U.S. troops tasked with eliminating North Korea's weapons of mass destruction are participating in military drills with South Korea, the top U.S. commander in the country said Thursday, according to 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. Sharp's comments came as the North has been escalating its rhetoric against the U.S. and South Korea over their ongoing annual military drills that began Monday. Pyongyang, which says they are a rehearsal for attack, warns it will bolster its nuclear capability and put its troops on high alert to cope with the drills. The U.S. says drills are purely defensive and that it has no intention to invade 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 the North to rejoin stalled six-nation talks. Also Thursday, South Korea's prime minister said North Korea must «listen to» international concerns over its atomic program and quickly return to negotiations. «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.