LONDON - Greece is relying on Iran for most of its oil as traders pull the plug on supplies and banks refuse to provide financing for fear that Athens will default on its debt.Traders said Greece has turned to Iran as the supplier of last resort despite rising pressure from Washington and Brussels to stifle trade as part of a campaign against Tehran's nuclear program.The near paralysis of oil dealings with Greece, which has four refineries, shows how trade in Europe could stall due to a breakdown in trust caused by the euro zone debt crisis, which is threatening to spread to further countries."Companies like us cannot deal with them. There is too much risk. Maybe independent traders are more geared up for that," said a trader with a major international oil company."Our finance department just refuses to deal with them. Not that they didn't pay. It is just a precaution," said a trader with a major trading house.