OPEC Secretary-General al-Badri waits for the start of a meeting of OPEC oil ministers at OPEC's headquarters in ViennaSaudi Arabia blocked calls on Thursday from poorer members of the OPEC oil exporter group for production cuts to arrest a slide in global prices, sending benchmark crude plunging to a fresh four-year low. Brent oil fell more than $6 to $71.25 a barrel after OPEC ministers meeting in Vienna left the group’s output ceiling unchanged despite huge global oversupply, marking a major shift away from its long-standing policy of defending prices. More