U.S. Marines based in Okinawa, Japan, aim their machine guns after landing in the landing operation during a South Korea and U.S. joint military exercise at Pohang beach, 400 kilometers (about 250 miles) southeast of Seoul, South Korea, Wednesday, Nov. 4, 2009. North Korea claimed Tuesday that it has successfully weaponized more plutonium for atomic bombs, a day after warning Washington to agree quickly to direct talks or face the prospect of a growing North Korean nuclear arsenal.