Most Opec ministers arriving in Vienna for today's emergency meeting voiced their support for a cut, but had widely divergent views about its size. The more hawkish nations want a cut of about 2m barrels a day while others favour a 750,000 b/d cut.

Saudi Arabia, the group's most powerful member has been quietly reducing its supplies over the past weeks, but has been lobbying for restraint. Opec's hawks – Venezuela and Iran – were pushing for a deeper reduction, while other countries supported a medium-size cut now and another probably in December.

Given the divergent views and rapid weakening oil demand, traders said investors had built financial positions, ahead of today's meeting which suggest they believe prices could fall as low as $50 by December.