Wall Street mostly rises as Fed holds key rate steady, deferring next likely hike to December

* Indexes: Dow up 0.10%, S&P 500 up 0.05%, Nasdaq off 0.13%

* Fed leaves rates unchanged, upgrades economic outlook

NEW YORK, Oct 28 (Reuters) - Wall Street stocks mostly rose on Wednesday after the US Federal Reserve left its key policy rate unchanged, as widely expected, shifting the probability of a rate hike to its next monetary policy meeting in December.

In its accompanying statement, the Fed upgraded its assessment of the economy while acknowledging inflation "remains elevated." At the press conference following the release, Fed Chair Kevin Warsh said the central bank has made clear its willingness and readiness to act.

"The Fed didn't throw any curveballs," said Ryan Detrick, chief market strategist at Carson Group in Omaha. "It was widely expected they'd hold, so no big surprise there."