Chevron Corp said on Thursday it expected second-quarter earnings to be hit by a sharp decline in U.S. refining margins, while better prices on the production side would be largely offset by foreign currency effects.

The second-largest U.S. oil company said the decline in second-quarter U.S. refining margins more than offset an increase in marketing margins, while margins were mixed outside its home country.

Refining margins have been squeezed by recovering crude oil prices, which increases input costs, and demand that is still weakened by the recession.

Chevron said U.S. oil-equivalent production in April and May was 682,000 barrels per day (bpd), up from 671,000 in the first quarter, while international output was 1.979 million bpd, down by 13,000 bpd from the previous quarter.

Chevron is targeting overall output of 2.63 million bpd for 2009. In late May, about 100,000 bpd of production in Nigeria had to be shut in due to violence. But a series of big projects are also starting up this year, including its Frade project off the coast of Brazil.

(Reporting by Braden Reddall; Editing Bernard Orr)