* Fed keeps rates steady, to start portfolio drawdown in October
* Statement suggests Fed still anticipates Dec rate hike
* Treasury yields jump to highest in 6 weeks
* Dow, S&P 500 end session with slight gains (Updates with closing U.S. market levels)
By Caroline Valetkevitch
NEW YORK, Sept 20 (Reuters) - U.S. Treasury yields and the dollar gained on Wednesday after the Federal Reserve signaled it expects one more U.S. interest rate hike by the end of the year.
Both the Dow and S&P 500 fell following the Fed statement but reversed those losses to end the session slightly higher and add to a string of closing records.
In its statement that followed a two-day meeting, the Fed, as expected, left rates unchanged and said it would begin in October to reduce its approximately $4.2 trillion in holdings of U.S. Treasury bonds and mortgage-backed securities.
Fed Chair Janet Yellen said in a press conference after the meeting that a fall in inflation this year remained a mystery and said the U.S. central bank was ready to change the rate outlook if needed.
Benchmark U.S. Treasury yields jumped to their highest in six weeks. Benchmark 10-year notes fell 9/32 in price to yield 2.27 percent, after yields got as far as 2.29 percent, the highest since Aug. 8.
Some traders and investors had thought the Fed might have struck a more dovish tone given the potential economic impact of recent severe hurricanes and still sluggish inflation.
The reaction in the Treasury market "suggests a lot of people maybe weren't anticipating the Fed would stick with the third rate hike expectation this year. So there's a little adjustment going on there," said David Joy, chief market strategist at Ameriprise Financial in Boston.
Interest rate futures traders are now pricing in a 68-percent chance of a December rate hike, up from around 60 percent before the statement, according to the CME Group's FedWatch Tool.
Financial shares added to gains following the statement, with the S&P 500 bank index ending up 0.7 percent, while utilities declined 0.8 percent.
The Dow Jones Industrial Average rose 41.79 points, or 0.19 percent, to end at 22,412.59, the S&P 500 gained 1.59 points, or 0.06 percent, to 2,508.24 and the Nasdaq Composite dropped 5.28 points, or 0.08 percent, to 6,456.04.
The Fed news is "kind of consistent with the view that the economy is doing OK, and as far as equity investors are concerned, another rate hike is not going to change that view," Joy said.
The pan-European FTSEurofirst 300 index lost 0.09 percent. MSCI's gauge of stocks across the globe gained 0.14 percent and hit another record high.
The dollar index rose 0.75 percent, with the euro down 0.03 percent to $1.1888.
Stocks had been mostly flat ahead of the Fed statement, while the dollar had been slightly lower.
Gold fell 1 percent following the Fed news after trading slightly higher ahead of the release. Spot gold was down 0.76 percent at $1,301.2 an ounce, trading back above $1,300.
Oil prices gained about 2 percent despite a rise in U.S. crude inventories.
Brent crude futures rose $1.15, or 2.1 percent, to settle at $56.29 a barrel, while U.S. crude futures gained 93 cents, or 1.9 percent, to settle at $50.41.
For Reuters Live Markets blog on European and UK stock markets see reuters://realtime/verb=Open/url=http://emea1.apps.cp.extranet.thomsonreuters.biz/cms/?pageId=livemarkets
Additional reporting by Karen Brettell in New York; Editing by Nick Zieminski and James Dalgleish