Gold is slightly more expensive on Tuesday morning, trading at $1,680 a troy ounce, supported by the value of some weakening of the dollar ahead of the U.S. Federal Reserve (Fed) meeting, trading data showed.

The price of December gold futures on the Comex New York exchange rose $2.6, or 0.15%, to $1,680.8 a troy ounce. December silver futures were up 0.65% to $19.483 an ounce.

The dollar index (exchange rate against a basket of currencies of the six U.S. trading partners) declined 0.09% to 109.64 points. A weaker dollar makes gold more affordable to buy in another currency.