The oil-exporting countries of OPEC have delayed the start of a meeting of oil ministers in Vienna.

Reports suggest they could not agree in advance what they should do to boost prices, which are at their lowest for twelve-years.

The BBC business correspondent says that when talks do begin, they're expected to focus on accusations that some OPEC members, including Venezuela and Iran, have not honoured an agreement made earlier this year for cuts in OPEC production.