US STOCKS-Wall St rallies, then fades, after Fed holds rates steady
* Fed leaves rates unchanged amid global concerns
* Indexes hit highs, then pare gains as Yellen takes questions
* Trading volatile after Fed statement
* Dow and S&P 500 close to unchanged; Nasdaq gains (Adds comment, updates prices)
By Sinead Carew
Sept 17 (Reuters) - Wall Street gave up a more than 1 percent rally on Thursday as investors struggled to interpret the Federal Reserve's decision to hold off on raising interest rates.
The U.S. central bank said global risks and other factors had convinced it to delay what would have been the first rate hike in nearly a decade but it left open the possibility of a modest policy tightening later this year.
Investors' focus turned to the next Fed meeting on Oct. 27-28 and they were still left to figure out the timing for the Fed's first benchmark rate increase since 2006.
The three major U.S. indexes all hit session highs, rising more than 1 percent for a while during Fed Chair Janet Yellen's 2.30 p.m. press conference. Trading right after the Fed's 2 p.m. statement release was choppy with the major U.S. indexes first hitting session highs and briefly turning negative before reversing course and turning positive again. Continuación...