ANZ Global Markets Commodity Research Analyst Natalie Robertson said top copper producer Codelco warned that copper stocks in China were "abnormally high and that non-mining companies were using copper as collateral for loans -- a significant risk to the downside."

Corn was weaker Tuesday morning amid technical profit-taking.

May corn was falling 0.6% to $7.55 ¾ a bushel, while soybeans for May delivery were falling 0.7% to $13.74 ½ a bushel.

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