June 10 (Bloomberg) -- Alcoa Inc., the world's third-largest aluminum producer, said its Australian alumina unit declared force majeure on its supply contracts because of a gas-supply disruption in Western Australia since June 3.

The financial impact on second-quarter earnings is expected to be 2 cents to 3 cents a share, New York-based Alcoa said today in a statement.

Alcoa and companies with operations in Western Australia including BHP Billiton Ltd. and Rio Tinto Group were left with reduced power supplies after a blast at an Apache Corp. plant cut natural-gas supplies by 30 percent.

Apache said on June 6 that its natural-gas output from Varanus Island may be halted for at least two months.

Alcoa rose 55 cents, or 1.3 percent, to $42.72 at 4:15 p.m. in New York Stock Exchange composite trading. The shares have gained 17 percent this year.

To contact the reporter on this story: Steven Frank in Toronto at sfrank9@bloomberg.net.

Last Updated: June 10, 2008 17:35 EDT