COMMODITIES-Wheat at 3-week highs, gas at 2-week peaks

* Fear of drier weather boosts U.S. wheat

* Gas rallies on frigid U.S. forecasts Platinum at 3-month high as Amplats cuts output

* Copper at 2-week low on U.S. debt ceiling, China worries

NEW YORK, Jan 15 (Reuters) - U.S. wheat prices hit three-week highs on Tuesday on fear that a return to dry weather could do further damage to grain in parched U.S. fields, and natural gas touched a two-week peak as colder weather boosted heating demand across the nation. Platinum extended the three-month highs from the previous session after a production overhaul by top global producer Anglo American Platinum cut world output by about 1 percent. Gold and silver also edged higher, boosting the precious metals complex. Copper hit a two-week low as worries over the U.S. debt ceiling resurfaced and the demand outlook from China looked cloudy. Other commodities such as orange juice, sugar, heating oil and crude oil also posted losses, weighing on the 19-commodity Thomson Reuters-Jefferies CRB index . Currency markets held little sway over commodities after the dollar fell against the yen and rose against the euro .

WHEAT LEADS GRAINS RALLY Wheat futures jumped 2 percent on the Chicago Board of Trade, rising for a third day, on fear that dry weather will return to the drought-stricken southern Plains, damaging dormant crops. Benchmark CBOT wheat for March delivery settled up 15-3/4 cents at $7.82-3/4 per bushel after racing earlier to $7.89-3/4, the highest price since Dec. 26. There was little rain or snow in the forecast in the Plains and western Midwest regions that grow most of the wheat in the United States, said Joel Widenor, an agricultural meteorologist for Commodity Weather Group. "Dry weather will prevail in core drought areas of the western Midwest and Central Plains through the last half of January," Widenor said. A cold snap this week may have caused some minor winterkill in areas of western Nebraska, and a blast of cold Arctic air is expected next week centered on the Midwest, said Don Keeney, a meteorologist for MDA EarthSat Weather. Conditions are expected to remain dry for the next two weeks in Argentina and southern Brazil, Keeney said. Corn and soybean futures were also higher, with corn on track for the seventh straight session of higher prices as conditions turned dry in Argentina, while the U.S. Agriculture Department's forecast last week for tight stockpiles continued to underpin prices.

PLATINUM EXTENDS 3-MONTH HIGHS Platinum rallied for a fifth straight session after Anglo American Platinum said it would mothball two South African mines and sell another. The overhaul by Amplats would cut output by around 400,000 ounces annually, accounting for nearly 1 percent of world output. The spot price of platinum jumped to nearly $1,700 an ounce, a high since Oct 9, before pulling to just below $1,680, a gain of 1.6 percent. Since the year began, the metal, used to remove toxins from auto fumes, has risen almost 10 percent. Platinum miners have been under intense pressure over the last year, hit by a wave of strikes while contending with rising operating costs and stubbornly depressed prices. Amplats' overhaul will involve cutting 14,000 jobs to restore profits, an action that may provoke a repeat of last year's strikes. "Anglo Platinum will not be the last company to cut output," S.P. Angel analyst John Meyer said. "We would expect platinum miners to pull back by 25 to 30 percent, which is going to have a severe impact on prices."

GAS SURGES ON FRIGID FORECASTS Natural gas futures rallied for a fourth straight day as colder weather made its way into U.S. consuming regions. "By this weekend, very cold weather is expected along major portions of the eastern half of the U.S., the coldest spell for this region so far this winter," said Energy Management Institute's Dominick Chirichella. Thomson Reuters Natural Gas Analytics data showed heating demand for the next two weeks would be close to normal, while the Northeast would see "enhanced" demand of about 57 heating degree days above normal. Degree days are a measure of departure in the mean daily temperature from 65 degrees Fahrenheit (18 degrees Celsius) and are used to estimate demand to heat or cool homes and businesses. Last week's much larger-than-expected inventory drawdown, the biggest in about two years, has kept gas prices to the upside, rising more than 9 percent in four trading days. New York's front-month gas futures contract settled up 2.4 percent at $3.455 per million British thermal units.

Prices at 3:27 p.m. EST (2027 GMT)

LAST/ NET PCT YTD CLOSE CHG CHG CHG US crude 93.44 -0.70 -0.7% 1.8% Brent crude 110.35 -1.53 -1.4% -0.7% Natural gas 3.455 0.082 2.4% 3.1%US gold 1683.90 14.50 0.9% 0.5% Gold 1681.20 14.40 0.9% 0.4% US Copper 363.75 0.35 0.1% -0.4% LME Copper 7994.00 -6.00 -0.1% 0.8% Dollar 79.696 0.208 0.3% 3.8%US corn 730.50 6.50 0.9% 4.6% US soybeans 1413.50 -4.50 -0.3% -0.4% US wheat 782.75 15.75 2.1% 0.6%US Coffee 152.50 -0.80 -0.5% 6.1% US Cocoa 2270.00 3.00 0.1% 1.5% US Sugar 18.62 -0.28 -1.5% -4.6%US silver 31.529 0.419 1.3% 4.3% US platinum 1688.00 31.70 1.9% 9.7% US palladium 713.35 10.05 1.4% 1.4%