GLOBAL MARKETS-Stocks rally, gold hits new high on Fed comment

* Stocks rebound as Fed opens door to raising money supply

* U.S. dollar extends decline vs euro after Fed statement

* U.S. gold futures hit new record high after Fed meeting

* Bond prices trim gains on Fed policy-makers' statement (Updates with market reaction following Federal Reserve policy-making meeting, adds byline)

By Manuela Badawy and Herbert Lash

NEW YORK, Sept 21 (Reuters) - World stocks rallied and gold prices hit new highs on Tuesday after the Federal Reserve opened the door to bolstering the struggling U.S. economy by increasing the money supply again.

U.S. Treasury yields fell after Fed policy-makers at the end of a one-day meeting failed left short term interest rates unchanged but said it would use all policy tools if needed to bolster a sluggish economic recovery. [ID:nNYE002900]

The Fed also underscored its concerns over slowing inflation in its statement on Tuesday, saying the underlying rate of inflation was below levels consistent with its mandate for price stability and full employment.

"This sets the table for QE (quantitative easing) in November or December should it be necessary. They are now outlining the key rationale for that -- low inflation, high unemployment," said Eric Green of TD Securities.

World stocks as measured by MSCI<.MIWD00000PUS> rebounded to trade 0.3 higher after the Fed statement.

Wall Street stocks also rallied. The Dow Jones industrial average <.DJI> was up 46.85 points, or 0.44 percent, at 10,800.47 late afternoon in New York. The Standard & Poor's 500 Index <.SPX> was up 2.07 points, or 0.18 percent, at 1,144.78. The Nasdaq Composite Index <.IXIC> was up 3.72 points, or 0.16 percent, at 2,359.55.

After its August meeting, the Federal Reserve issued a bleak assessment of the economy and the S&P 500 stock index tumbled more 4.0 percent over the next four days.

"The across-the-board rally is consistent with markets seeing the Fed as both able and willing to stimulate sufficient growth and stable inflation," said Mohamed El-Erian, co-chief investment officer at Pacific Investment Management Co., which oversees more than $1 trillion in mostly fixed-income assets.

While stocks rallied on hopes that the Fed would boost economic growth, gold prices spiked to a new high on fears that government deficit spending and higher growth rates will spur inflation. Spot gold prices rose to a new record high around $1,288.50.

The benchmark 10-year U.S. Treasury note gained 28/32 in price, driving its yield down to 2.60 percent on the prospect of further Federal Reserve purchases of U.S. debt.

The U.S. dollar was down against a basket of major currencies, with the U.S. Dollar Index <.DXY> down 1.10 percent at 80.439.

The euro was up 1.35 percent at $1.3241, while against the Japanese yen, the dollar was down 0.75 percent at 85.04. (Reporting by Jennifer Ablan, Rodrigo Campos, Chris Kelly, Richard Leong and Nick Olivari in New York; Writing by Herbert Lash)