The SPDR S&P 500 ETF (NYSEArca: SPY) was off 0.6% in premarket action Tuesday as U.S. stocks were set to open down following disappointing earnings from Alcoa and a sell-off in the commodities market.

Alcoa started the first-quarter earnings season with a thud.

Also, the pullback in crude-oil prices this week drove investors to take profits in risky assets such as equities, according to a report Tuesday.

“Open interest has been building up since the start of the new quarter in April, reflecting fresh inflows of speculative money into the oil market,” an energy analyst told Reuters. “The Goldman report put a damper on this flow, at least for now, given that there was a sense of an overshoot in the market.”

U.S. Oil Fund (NYSEArca: USO) fell over 3% Monday following news of peace talks in Libya while Goldman Sachs strategists closed a commodities trade they had initiated in late 2010.

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