Prices fell by up to 5 percent on Tuesday after the International Monetary Fund cut its 2015 global economic forecast and OPEC member Iran hinted at further price weakness, saying its oil industry could withstand $25 oil. Russia has refused to cut production with OPEC, but Deputy Prime Minister Arkady Dvorkovich said on Wednesday that oil output may see a natural decline of as much as 1 million barrels per day (bpd).