NEW YORK (MarketWatch) -- Gold futures slumped Tuesday, hitting their lowest level in nearly four weeks, on concerns the Federal Reserve will signal it is prepared to begin slowing the flow of monetary stimulus to the economy. Gold for August delivery gcq3 dropped $16.20, or 1.2%, to close at $1,366.90 an ounce in Nymex floor trade, after dipping to $1,360.20, the lowest level for a most-active contract since May 23, according to FactSet. The Fed will conclude a two-day policy meeting on Wednesday, followed by a news conference hosted by Fed Chairman Ben Bernanke. July silver SIN23, dropped 8 cents to close at $21.68 an ounce, while July platinum pln3 rose $5.30 to settle at $1,440.10 per ounce.