CHICAGO: Chicago corn prices surged to a four-week high on Thursday as forecasts of warmer weather and worries over recent storm damage in the US Midwest countered pressure from recent government forecasts calling for a massive US harvest.

CBOT December corn ended up 11-1/2 cents, settling at $3.38-3/4 per bushel - and touched its highest price in mid-day trading since July 13.

Traders said a recent slide in corn, which led the European Union this week to re-introduce a corn import tariff, also was helping to fuel Thursday's price rally for US supplies.

Traders also said there is a shift in the market's focus - from being driven by a bearish outlook on supply and weather, to the beginning of a bullish outlook over crop conditions and the potential for rising export demand.

USDA said export sales of corn for the week ended Aug. 6 totaled 930,300 tonnes (old and new crop years combined), in line with trade expectations for 400,000 to 1.4 million tonnes.