Chevron executives are renewing efforts to have Ecuador's preferential trade status with the U.S. revoked next month…Chevron and its subsidiary Texaco have been locked in a legal battle in the South American country since 1993 when…residents of Lago Agrio sued Texaco, maintaining that American oil exploration and extraction had created an "Amazonian Chernobyl." Chevron executives expect an Ecuadorean court to file soon a judgment against them in the class-action suit…The company says the judgment…should give the U.S. grounds to cancel Ecuador's benefits under the Andean Trade Preferences Act…But Chevron faces a large hurdle in the form of Mr. Obama…The U.S. Chamber of Commerce, which Chevron counts as an ally, said revoking Ecuador's trade status is unlikely.