* Fed leaves rates unchanged, lowers economic growth forecast
* Fed Chair Janet Yellen to speak at 2:30 p.m. EDT
* May producer price index up 0.4 pct vs est 0.3 pct
* Indexes up: Dow 0.37 pct, S&P 0.36 pct, Nasdaq 0.36 pct (Updates to with detail after Fed statement)
By Noel Randewich
June 15 (Reuters) - Wall Street maintained gains on Wednesday after the Federal Reserve left its key interest rate unchanged, as expected, but signaled it still plans two rate increases this year.
The U.S. central bank also lowered its economic growth forecasts for 2016 and 2017 and indicated it would be less aggressive in tightening monetary policy after the end of this year.
Fed Chair Janet Yellen is scheduled to hold a press conference at 2:30 p.m. (1830 GMT).
"It's as dovish as the Fed can get without actually cutting rates," said Brian Jacobsen, chief portfolio strategist at Wells Fargo Funds Management in Menomonee Falls, Wisconsin.
While traders had discounted a rate increase this month, they have been eager for clues about the health of the economy and the trajectory of future hikes.
Investors have become more nervous ahead of a vote in Britain next week on whether to leave the European Union, with recent opinion polls indicating growing support for such a move.
At 2:04 pm (1804 GMT) the Dow Jones industrial average was up 0.37 percent at 17,740.15 and the S&P 500 had gained 0.36 percent to 2,082.83.
The Nasdaq Composite added 0.36 percent to 4,861.23.
Eight of the 10 major S&P sectors were higher, led by the materials index, up 1 percent. (Additional reporting by Yashaswini Swamynathan in Bengaluru; Editing by James Dalgleish)