(Reuters) - Two U.S. B-1B bombers took part in joint U.S.-South Korean military drills on Thursday, an official at Seoul s defense ministry told Reuters, exercises which North Korea has said are taking the peninsula to the brink of nuclear war.  The planes, which scrambled from a U.S. air base in Guam, joined some 20 fighter aircraft of the two countries which have been staging a large-scale aerial exercise in South Korea since Monday, the official said. One bomber joined the exercises on Wednesday.  
Two U.S. B-1B bombers join U.S.-South Korean military drills