Gold edged higher on Thursday on persistent worries about euro zone debt woes and slower global growth, defying a rebound in the U.S. dollar.

The dollar index rose nearly 0.4 percent, after dropping to a three-week low in the previous session, as the Swiss franc fell on talks that the Swiss National Bank stepped up measures to curb the strength of the safe-haven currency.

Investors, disappointed by this week's Franco-German summit on the lack of an effective solution to the euro zone's debt crisis and wary of sluggish global growth prospects, continued to seek security in bullion.

Spot gold gained 0.3 percent to $1,793.70 an ounce by 06:46 GMT, headed for a fourth session of gains. It was only 1.1 percent below its all-time high of $1,813.79 struck last week.

U.S. gold edged up 0.2 percent to $1,796.80.

"Gold is stabilizing in the near term," said Ronald Leung, a physical dealer at Lee Cheong Gold Dealers in Hong Kong.

"But low interest rates in the United States and the messy situation in Europe will push gold higher."

Leung said physical buying was muted as prices advanced towards the record high, with investors waiting for a price dip.

Gold-backed exchange-traded funds continued to draw interest. Holdings in the SPDR Gold Trust , the world's largest gold ETF, rose by 0.72 percent on the day to 1,271.985 metric tons by Aug. 17.

The Relative Strength Index on spot gold remained above 70, which suggests the underlying asset has been overbought, although it has been in this territory for nearly two weeks.

Technical analysis suggested that gold faces resistance at $1,793 an ounce, said Reuters market analyst Wang Tao.

But gold's bull run still has momentum.

"Although profit-taking, margin requirement hikes and seasonally soft physical demand could temper the rally intermittently, the external environment has turned increasingly fertile for gold," said Barclays Capital in a research note.

Gold's fortunes could be altered in the case of rising real interest rates, controlled inflation and a stable macro-environment, it added.

Gold demand fell in the second quarter but is expected to rise in the full year as Asian buyers add to holdings and safe haven demand grows, said the World Gold Council.

Spot silver gained half a percent to $40.36 an ounce, after closing above $40 for the first time in two weeks in the previous session.

Holdings in the iShares Silver Trust , the world's largest silver ETF, edged higher to 9,727.10 metric tons by Aug. 17, the trust said.

"The sentiment in silver is still weak even though prices are climbing slowly," said a Tokyo-based trader.

He added that although a gold rally traditionally encourages silver prices to rise, the poor economic outlook has weighed on demand prospects of the metal, which has wide industrial applications.

"The 20-day moving average has been a decent support and the rising channel seems in place, but it will be difficult for silver to breach $42 unless gold advances towards $1,850."

Spot platinum held steady at $1,836, after rising for seven sessions straight.