US STOCKS-S&P 500 ends slightly higher after Fed gives mixed signals

(For a live blog on the U.S. stock market, click or type LIVE/ in a news window.)

* Market rebounds late in session

* Roku drops after Comcast offers free gadgets to customers

* FedEx tumbles after dismal full-year profit forecast

* Indexes: Dow +0.13%, S&P 500 +0.03%, Nasdaq -0.11% (Updates with close)

By Noel Randewich

Sept 18 (Reuters) - The S&P 500 ended marginally higher on Wednesday after Federal Reserve policymakers cut interest rates by a quarter of a percentage point, as expected, but gave mixed signals about their next move.

With continued economic growth and strong hiring "the most likely outcomes," the Fed nevertheless cited "uncertainties" about the outlook and pledged to "act as appropriate" to sustain the expansion.

New projections showed policymakers at the median expected rates to stay within the new range through 2020, bad news for investors hoping for additional cuts to help blunt global economic fallout from the U.S.-China trade war.

Stocks sold off immediately after the Fed's announcement but rebounded during Chairman Jerome Powell's press conference. He told reporters the Fed was prepared to be "aggressive" if necessary.

"He did a very good job conveying the view that this was a mid-cycle adjustment, but that obviously the Fed is ready to act if it needs to do more," said Mike O’Rourke, chief market strategist at JonesTrading.

The late-session rebound could be partly the result of short sellers covering their positions after the earlier dip, O'Rourke said.

Of the stock bounce, Cherry Lane Investments partner Rick Meckler said, "The bottom line is (Powell) didn't say anything that negative. You think about what he presented, it's status quo. People thought about it, they thought about the fact that rates are going lower, that normally is supportive for stocks."

Expectations of lower rates have supported Wall Street's rally this year, with the benchmark S&P 500 up almost 20% year to date and about 1% below its record high close in July. The Dow Jones Industrial Average rose 0.13% to end at 27,147.08 points, while the S&P 500 gained 0.03% to 3,006.73.

The Nasdaq Composite dropped 0.11% to 8,177.39.

Six of the 11 major S&P sectors climbed, led by a 0.5% increase in the S&P utilities index and a 0.4% rise in the financial index.

The interest-rate sensitive S&P 500 banks index rose 0.7%.

The central bank also widened the gap between the interest it pays banks on excess reserves and the top of its policy rate range, a step taken to smooth out problems in money markets that prompted a market intervention by the New York Fed this week.

FedEx shares tumbled 12.9%, posting their deepest one-day percentage drop since the financial crisis after the company blamed U.S.-China trade tensions and a split with Amazon.com Inc for its dismal full-year profit forecast.

Roku slumped 13.7 after Comcast said it will offer its own streaming media set top box for free to its U.S. internet-only customers.

Beyond Meat dropped 3.9 after Restaurant Brands International Inc's Tim Hortons cut the faux meat maker's burgers and sandwiches from its menu in most Canadian provinces, months after a nationwide roll-out at the breakfast chain.

Declining issues outnumbered advancing ones on the NYSE by a 1.21-to-1 ratio; on Nasdaq, a 1.52-to-1 ratio favored decliners.

The S&P 500 posted 19 new 52-week highs and 1 new lows; the Nasdaq Composite recorded 42 new highs and 38 new lows.

Volume on U.S. exchanges was 6.7 billion shares, compared with the 6.9 billion-share average over the last 20 trading days. (Additional reporting by Medha Singh and Ambar Warrick in Bengaluru Editing by Nick Zieminski, David Gregorio and Tom Brown)