U.S. companies are increasingly less optimistic about the business outlook in China, and see growing competition from local rivals who get preferential treatment as a key challenge, a survey showed on Friday. A US-China Business Council survey of senior executives at its 200-plus member companies showed ebbing optimism about the five-year business outlook for China, which is grappling with slowing economic growth. The 2014 survey, which will be formally released on Monday, showed 31 percent of respondents were "optimistic" about the mid-term outlook, compared with 39 percent in 2013, although the share of those saying they were "somewhat optimistic" rose. Eighty-three percent said their Chinese operations were profitable, down from 91 percent in 2013. Half planned to increase resources invested in China in the next 12 months.