Indirect talks between Tehran and Washington on reviving the 2015 Iran nuclear deal resumed in Vienna as the European Union said negotiations were "intense" and Germany called for rapid progress. The sixth round of talks began as usual with a meeting of remaining parties to the deal - Iran, Russia, China, France, Britain, Germany and the European Union - in the basement of a luxury hotel. The talks' chief coordinator, EU foreign policy official Enrique Mora, who is leading the shuttle diplomacy between Iran and the United States, has said he expects a deal in this round of talks. Other envoys, however, are more cautious, saying many difficult issues are yet to be resolved.