Gold fell more than one percent on Tuesday from 15-week highs scored the previous day as investors took profits ahead of the release of key U.S. data, dealers said.

Platinum slipped to a three-week low before rebounding, while silver and palladium were little changed.

"Unless the dollar starts to weaken significantly again, the market does seem to have done enough for the time being," said Simon Weeks, director of precious metals at ScotiaMocatta.

If gold failed to get back above $640-$642, prices might drop to around $630 -- the level in the middle of last week when U.S. traders left the market ahead of the Thanksgiving holiday, he said.

Investors awaited comments from Federal Reserve Chairman Ben Bernanke on the economic outlook due at 1730 GMT and U.S. third-quarter gross domestic product data due on Wednesday.

Spot gold hit a high of $641.70 an ounce before falling to $632.80/633.45 by 1528 GMT, against $640.60/641.60 in New York late on Monday, when prices rose to their highest since mid-August.

Profit-taking might persist, but prices were unlikely to drop sharply in the coming days, dealers said.

"Overall, the broad macroeconomic context looks positive for gold at present, but further gains from here will continue to be highly reliant on the future path of the dollar," Barclays Capital said in a daily report.

Gold moved lower despite weakness in the dollar, which fell to a fresh 20-month low against the euro before paring losses.

Gold often moves in the opposite direction to the dollar.

Despite selling by gold investors on Tuesday, UBS Investment Bank forecast the price at $660 in a month and at $690 three months from now.

TheBullionDesk.com said in a note that chart resistance around $640-$642 and caution ahead of Bernanke's address was curbing gold's bullish sentiment.

"However, the metal's increasing correlation with the euro and return of investor money, as players begin to diversify away from the greenback, should see gold challenge $650 and eventually $685 before year-end," it said.

In other metals, platinum dropped as low as $1,130 an ounce before rising to $1,155/1,165, compared with $1,140/1,150 in the U.S. market. Prices have fallen 19 percent since touching a record high of $1,395 last week.

Silver edged down to $13.42/13.49 an ounce from $13.46/13.53, while palladium was down $1 at $322/327.