OPEC agrees to boost oil output by 500,000 barrels a day

VIENNA, Austria -- OPEC sought to reassure jittery oil markets Tuesday by agreeing to boost crude production by 500,000 barrels a day, a move the cartel conceded was prompted partly by "clouds on the horizon" from the U.S. housing slump. The Organization of Petroleum Exporting Countries said the higher output would begin Nov. 1. It pledged to "vigilantly monitor" the other factors buffeting crude markets, including worries that supplies might not keep pace with higher demand later this year as it becomes winter in the Northern Hemisphere. Significantly, the 12-nation cartel said the increase would be based on current production, meaning it will add real oil to the market. In the recent past, OPEC has raised only its official output quota; because it tends to pump over those targets, the increases were purely cosmetic.