Spot gold was up 0.4% to $1,963.97 per ounce by 1131 GMT, while U.S. gold futures rose 0.4% to $1,973.50 per ounce.
"What we're probably seeing building in gold here is the expectation that the Fed is going to be more dovish than in the past, and the realization that we're seeing slightly more inflationary pressure than anticipated," said OANDA analyst Craig Erlam.
While the Fed does not need to announce stimulus measures now, it will have to lay the groundwork for potential stimulus later, he added.
Making bullion more attractive for those buying the metal in other currencies, the dollar index fell in the run-up to the Fed decision at 1800 GMT.
The meeting is its first since the central bank took a more relaxed stance on inflation last month. The policy announcement will be followed by a news conference by Chairman Jerome Powell half an hour later.
"Markets will want to see if the Fed will modify its language as some expect, perhaps something to the effect that it will keep rates low for a period of time (say three years) or maybe do the same thing with its inflation language," ED&F Man Capital Markets analyst Edward Meir said in a note.
"But, we doubt the Fed will lock itself into such a fixed language ahead of a potential turn in the U.S. economy."
Lower U.S. interest rates tend to weigh on bond yields and the dollar, bolstering the appeal of non-yielding gold, which is also seen as hedge against inflation and currency debasement.
Elsewhere, silver rose 0.1% to $27.27 per ounce, while platinum fell 0.9%, to $969.83 and palladium slipped 1.2% to $2,381.82 per ounce.
By Nakul Iyer
