US soldiers wear chemical warfare gear during a joint military exercise with South Korea at a US Army base in Dongducheon, 40kms north of Seoul, on March 3, 2011 aimed to simulate the detection and disposal of North Korea's chemical, biological, radiological and nuclear weapons. US and South Korean soldiers displayed their techniques for handling weapons of mass destruction (WMD) in the face of North Korea's nuclear sabre-rattling.

A South Korean soldier sits on the top of an armoured vehicle during a joint military exercise with the US at a US Army base in Dongducheon, 40kms north of Seoul, on March 3, 2011 aimed to simulate the detection and disposal of North Korea's chemical, biological, radiological and nuclear weapons.

US soldiers wearing chemical warfare clothing walk in smoke during a joint military exercise at a US Army base in Dongducheon, 40 kms north of Seoul, on March 3, 2011 aimed to simulate the detection and disposal of North Korea's chemical, biological, radiological and nuclear weapons.

US soldiers wearing chemical warfare gear check a sample during a joint military exercise with South Korea at a US Army base in Dongducheon, 40kms north of Seoul, on March 3, 2011 aimed to simulate the detection and disposal of North Korea's chemical, biological, radiological and nuclear weapons. US and South Korean soldiers displayed their techniques for handling weapons of mass destruction (WMD) in the face of North Korea's nuclear sabre-rattling.

A US soldier wears chemical warfare gear during a joint military exercise with South Korea at a US Army base in Dongducheon, 40kms north of Seoul, on March 3, 2011 aimed to simulate the detection and disposal of North Korea's chemical, biological, radiological and nuclear weapons. US and South Korean soldiers displayed their techniques for handling weapons of mass destruction (WMD) in the face of North Korea's nuclear sabre-rattling.

U.S. soldier from the 2nd Infantry Division wearing gas mask and anti-chemical gears, checks their gears during a joint military military drill between U.S. and South Korea for chemical, biological, radiological and nuclear detection and response capabilities at U.S. military base, Camp Casey in Dongducheon, north of Seoul, South Korea, Thursday, March 3, 2011.

A US soldier wears chemical warfare gear during a joint military exercise with South Korea at a US Army base in Dongducheon, 40kms north of Seoul, on March 3, 2011 aimed to simulate the detection and disposal of North Korea's chemical, biological, radiological and nuclear weapons. US and South Korean soldiers displayed their techniques for handling weapons of mass destruction (WMD) in the face of North Korea's nuclear sabre-rattling.