The dollar could collapse if Opec officially admits considering changing the pricing of oil into alternative currencies such as the euro, the Saudi Arabian foreign minister has warned. Prince Saud Al-Faisal was overheard ruling out a proposal from Iran and Venezuela to discuss pricing crude in a private meeting at the oil cartel's conference. In an embarrassing blunder at the meeting in Riyadh, ministers' microphones were not cut off during a key closed meeting, and Prince Al-Faisal was heard saying: "My feeling is that the mere mention that the Opec countries are studying the issue of the dollar is itself...