By Jeff Mason and Bruce Wallace RANCHO MIRAGE, Calif. (Reuters) - U.S. President Barack Obama and allies from Southeast Asia will turn their attention to China on Tuesday on the second day of a summit intended to improve commercial links and provide a united front on maritime disputes with Beijing. After a first day focused on trade and economic issues, Obama and his counterparts from the Association of Southeast Asian Nations (ASEAN) will try to arrive at a common position on the South China Sea during a second day of talks at Sunnylands, a California resort. China and several ASEAN states have conflicting and overlapping claims in the South China Sea, but not all the Southeast Asian nations agree on how to handle them.