The U.S. consumer confidence in September rose to the highest level in four months, indicating an optimistic outlook of the U.S. economy, according to the Thomson Reuters/ University of Michigan index of consumer sentiment revealed on Friday.

The index of U.S. consumer confidence climbed to 78.3 in September from 74.3 in the prior month, the best reading since May, when the index stood at 79.3.

The index gauging consumer expectations for six months from now, which more closely projects the direction of consumer spending, increased to 73.5 from 65.1 in August. The index of current conditions, reflecting Americans' perceptions of their financial situation and whether they consider it a good time to buy big- ticket items like cars, fell to 85.7 from 88.7 last month.

"The September improvement in confidence was due to more favorable prospects for the economy and for jobs during the year ahead," said Richard Curtin, chief economist in charge of the survey.

Rising property values, higher stock prices and a stabilization in the cost of gasoline may all contribute to drive sentiment up. Growing confidence could stimulate consumer spending. It is widely believed that the U.S. economic recovery will heavily rely on the rebound of consumer spending, which accounts for about 70 percent of the overall economic activity.