The move was expected as Qatar has been supplying both grades to customers at full contracted volumes since August 2009, the source said.

Qatar gave buyers an option of asking for cargoes to be 5 percent more or less than contracted volumes, unchanged from the previous month, the source added.

Oil refiners are expected to decide whether to exercise the option after top supplier Saudi Arabia notifies buyers of its October supplies as early as next week.

Copyright Reuters, 2011