Gold falls in line with euro * No boost from softer U.S. data * Gold/platinum ratio rises to two-month high (Updates with comment, refreshes prices) By Jan Harvey April 17 (Reuters) - Gold slipped on Tuesday, falling for a third day in its longest losing streak in a month, after a bout of technical selling pushed down the price, while a decline in the euro weighed even more on the market. Spot gold was down 0.5 percent on the day at $1,643.91 an ounce at 1437 GMT, while U.S. gold futures for June delivery fell 0.6 percent, or $10.1, to $1,639.70. Prices have fallen by over 2 percent in the last three days as the euro has been undermined by worries over euro zone debt. While these concerns supported gold as a safe haven last year, in recent months, currency pressures have proved a more important driver. The euro fell against most currencies as a generally solid Spanish bill auction and an upbeat report on German investor sentiment failed to ease concerns about prospects for the region's economy. "We've not had any good news for gold in a while," Matthew Turner, analyst at Mitsubishi said. "In that sense, you might say the price is holding up quite well." "But if the euro crisis can't spark safe-haven demand, then you'd have to think nothing would ... You've got countries that might have to depreciate, devalue or default. Those are the three things gold is supposed to protect against, but the problem is it gets bound up with the euro falling and that blunts its appeal." Gold's correlation to the single European currency is close to its most positive since late last year, around +64 percent, meaning that it is more likely to move in tandem with the euro than against it. The correlation between the two was negative for many of the final weeks of 2011. "Gold, on the balance of probabilities, will continue to be correlated with the euro/dollar," RBS analyst Nikos Kavalis said. "Bad news for Europe for the time being will be bad news for gold, and I can't see this changing unless there is a very dramatic development." Spain sold slightly more treasury bills than expected in an auction, which is an important precursor to a Spanish sale of benchmark 10-year bonds on Thursday. FOCUS ON SPAIN Concerns about Spain's finances kept the overall mood cautious and volumes low, however. A dramatic worsening of the situation in the euro zone could support gold in the longer term as a haven from risk, analysts said. U.S. data on factory output and housing construction fell short of expectations, which should have offered gold a boost, but the euro succumbing to investor concern over the debt crisis offset any potential lift to the bullion price. Physical gold demand has softened a touch this year from last year's levels. American Eagle gold coin sales from the U.S. Mint fell 30 percent in the first quarter, and demand in India, historically the world's biggest gold consumer, has been light. India's central bank cut interest rates on Tuesday for the first time in three years by an unexpectedly sharp 50 basis points to give a boost to sagging economic growth. If this stimulates growth, it is likely to prompt more gold buying. "The unexpected lowering of the interest rate in India could lend support by increasing the hitherto weak demand for gold in the country," Commerzbank said. Among other precious metals, silver was up 0.4 percent at $31.56 an ounce, spot platinum was flat at $1569.74 an ounce. The platinum/gold ratio, or the number of gold ounces needed to buy an ounce of platinum, rose to a two-month high at 1.05 on Tuesday. As an investment vehicle, gold is finding more support in the current climate than industrial metal platinum, which is heavily exposed to the European car market. "Platinum lacks safe-haven status and has limited investment demand. With jewellery and the automotive industry as key end markets, slowing global GDP and lower discretionary spending put demand at risk," Morgan Stanley said in a weekly note. Both platinum and palladium are used in catalytic converters. A heavier loading of platinum is used in the diesel autocatalysts most commonly seen in Europe, while the petrol engines favoured in the United States and China carry a heavier loading of palladium. Platinum's ratio to palladium also fell back to its lowest in a month, with an ounce of platinum now equivalent to 2.41 ounces of palladium, down from 2.5 a week ago. (Additional reporting by Amanda Cooper; editing by xxxx)

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