July 27 (Reuters) - U.S. stocks opened slightly lower on Tuesday ahead of earnings reports from the most valuable companies on Wall Street and in the run-up to the two-day Federal Reserve meeting. The Dow Jones Industrial Average fell 65.41 points, or 0.19%, at the open to 35,078.90. The S&P 500 opened lower by 5.92 points, or 0.13%, at 4,416.38. The Nasdaq Composite dropped 32.77 points, or 0.22%, to 14,807.95 at the opening bell. (Reporting by Ambar Warrick; Editing by Arun Koyyur) Our Standards: The Thomson Reuters Trust Principles.