U.S. stock index futures edged lower on Tuesday, indicating the benchmark S&P index may fall for a third straight session after a warning from the IMF about global growth prospects.
* Earnings season gets underway in the United States when Dow component Alcoa Inc reports quarterly earnings. Analysts expect Alcoa's third-quarter results to show it broke even, down from a profit of 15 cents per share a year earlier, according to Thomson Reuters data.
* Analysts forecast third-quarter earnings of Wall Street's S&P 500 companies would fall 2.3 percent from the year-ago quarter, according to Thomson Reuters data, which would be the first drop in U.S. quarterly earnings in three years. According to the data, 91 companies in the S&P 500 have issued negative outlooks versus 21 positive pre-announcements, for a ratio of 4.3, the weakest showing since the third quarter of 2001.
* Recent earnings warnings from large multinationals such as FedEx Corp , Caterpillar Inc and Hewlett-Packard Co which have cited weakness in Europe and China have left investors cautious about the prospects for corporate profits.
* Edwards Lifesciences Corp cut its revenue forecast for the third quarter, as sales of the medical device maker's unique heart valve that was expected to drive results fell short of estimates.
* European shares gave up early gains and turned negative as concerns over slowing global growth and its impact on corporate earnings weighed, although charts signaled a bounce back.
(Reporting by Chuck Mikolajczak Editing by W Simon)