European Factors to Watch-Shares seen higher, focus on earnings

LONDON, July 9 (Reuters) - European shares were expected to extend gains on Tuesday, tracking Wall Street and markets in Asia, with growing optimism about the health of the U.S. economy and a good start to the earnings season boosting sentiment. Alcoa, the largest U.S. aluminum producer, posted a larger-than-expected adjusted second quarter profit on Monday due to productivity gains and a strong performance from its engineered products business. "Alcoa has kicked off the earnings season