* Corn pressured by a firm dollar, weak crude oil and lower equities due to concern about the fate of the global economy amid mounting worries over the euro zone debt crisis. * Declines were slowed by spillover support from firm soybeans amid outlooks for warmer and drier weather in portions of South America's corn and soybean growing areas. * In Argentina, showers were limited to northwest fringes on Tuesday and just be scattered through southern and western areas this weekend. The northeastern third of the corn and soybean belt may see some expanding moisture deficits by late in the month, particularly Santa Fe, Entre Rios and northeastern Buenos Aires - Commodity Weather Group. * There was some relief for a small group of Chicago grain traders caught in the fallout of MF Global's collapse, as they were able to close out positions more than a month after the broker's bankruptcy. * The US Agriculture Department is expected to lower its forecast of US corn stocks slightly due to rising feed use and a lackluster harvest and raise its soy supply outlook by nearly 10 percent because of poor export demand, according to analysts' surveyed by Reuters. USDA will release its December crop report at 7:30 a.m. CST (1330 GMT) on Friday.