* Option expiry, weak data send gold to lowest since May
* Gold posts biggest one-day loss in almost a month
* Bullion at risk to break below two-year support channel
* Coming up: U.S. June durable goods data on Wednesday
(Recasts, adds comments, updates prices, changes byline, dateline, previous LONDON)
By Frank Tang
NEW YORK, July 27 (Reuters) - Gold dropped 2 percent on Tuesday to a near three-month low under $1,160 an ounce, as weak consumer confidence data and an option expiration triggered heavy technical selling.
After trading modestly weaker in early sessions, bullion prices accelerated losses to hit a low of $1,157.65 an ounce, the cheapest price since May 5 despite firm U.S. stock markets and a flat dollar. Gold also posted also its biggest one-day decline since July 1.
Silver and platinum group metals tracked gold and crude oil to fall sharply after data showed stagnant growth of U.S. home prices and as job worries drove July U.S. consumer confidence to its lowest since February. [
]Sean Lusk, market specialist at Chicago-based futures broker PFGBest, said that dealers sold heavily in an attempt to push gold futures prices lower as COMEX August gold options were expiring on Tuesday.
Gold prices sometimes gravitate toward an option strike price as traders try to profit from their bets when options are about to expire.
"In conjunction with the option expiration here, you have a lot of longs liquidating and rolling into another forward months," Lusk said.
Price volatility has spiked ahead of August's first-notice day on Friday, as gold investors rolled their August futures into December contracts, traders said.
Spot gold <XAU=> was at $1,160.15 an ounce at 2:29 p.m. EDT (1829 GMT), against $1,183.75 late in New York on Monday. U.S. gold futures for August delivery <GCQ0> settled at a three-month low at $1,158 an ounce, down $25.10.
Gold also looked vulnerable on technical charts. Bullion prices are at risk of breaking below a two-year bullish support channel and could fall toward $1,000 an ounce, CitiFX said. [
]If gold prices close the week below the two-year rising support line at around $1,176, it would point to extended losses. A divergence on weekly charts, where oscillators like the RSI did not make a new high when gold was hitting its record high at $1,264.90 an ounce last month, was also bearish, CitiFX said.
(Graphic: http://link.reuters.com/duw79m)
A weekly close through the base of the channel could lead to loses toward $1,030-1,045, a level last seen in February.
GLD OUTFLOW DENTS SENTIMENT
A decline in holdings of the world's biggest gold ETF, SPDR Gold Trust <GLD>, suggests the investment demand that drove prices earlier in the year is waning, analysts said. The trust has recorded an outflow of 18.7 tonnes of gold so far this month. [
]The metal rose to an all-time high of $1,264.90 an ounce in June as concerns over sovereign debt levels in the euro zone fueled buying of the metal as a haven from risk, but has struggled to hold those levels as such fears recede.
Sentiment turned weaker after India's central bank raised interest rates more strongly than expected, in the face of inflation that has held above 10 percent for the past five months. India is the world's biggest gold buyer [
]Gold priced in euros and sterling also fell on Tuesday. Euro-priced gold <XAUEUR=R> fell to its weakest since May 4 at 892.23 euros an ounce, while sterling-denominated bullion <XAUGBP=R> reached a three-month trough at 744.30 pounds an ounce.
Among other precious metals, silver <XAG=> was at $17.63 an ounce against $18.14, platinum <XPT=> was at $1,530.50 an ounce versus $1,548.25 and palladium <XPD=> at $465 versus $471.70. Prices at 2:57 p.m. EDT (1857 GMT)
LAST/ NET PCT YTD
CLOSE CHG CHG CHG US gold <GCQ0> 1158.00 -25.10 -2.1% 5.6% US silver <SIU0> 17.626 -0.574 0.0% 4.6% US platinum <PLV0> 1536.70 -19.10 -1.2% 4.5% US palladium <PAU0> 466.55 -8.45 -1.8% 14.1% Gold <XAU=> 1160.25 -23.50 -2.0% 5.8% Silver <XAG=> 17.60 -0.54 -3.0% 4.5% Platinum <XPT=> 1529.00 -19.25 -1.2% 4.3% Palladium <XPD=> 464.50 -7.20 -1.5% 14.5% Gold Fix <XAUFIX=> 1168.00 -16.00 -1.4% 5.8% Silver Fix <XAGFIX=> 18.16 15.00 0.8% 6.9% Platinum Fix <XPTFIX=> 1560.00 2.00 0.1% 6.4% Palladium Fix <XPDFIX=> 478.00 2.00 0.4% 18.9% (Additional reporting by Jan Harvey in London; Editing by Marguerita Choy)