The international gold and foreign exchange reserves held by the world’s biggest oil-producing nations in the EU could be at risk, Russian President Vladimir Putin said on Friday, after EU leaders discussed using frozen Russian assets to help Ukraine. “This is not just a blow to its image; it is an undermining of trust in the euro zone,” Putin said in year-end remarks to the Russian press, as carried by Reuters. “The fact is that many countries keep their gold and foreign exchange reserves in the euro zone, not…