UNITED NATIONS, Dec 14 (Reuters) - The door to resuscitating the 2015 Iran nuclear deal is open for now but "we are rapidly reaching the end of the road" to revive a pact that is being gutted by Iran"s nuclear advances, France"s ambassador to the United Nations said on Tuesday. "We are nearing the point where Iran"s escalation of its nuclear program will have completely hollowed out the JCPOA," Nicolas de Riviere told reporters, referring to Iran"s 2015 Joint Comprehensive Plan of Action deal with six powers - Britain, China, France, Germany, Russia and the United States. "Iran has to choose between the collapse of the JCPOA and a fair and comprehensive deal...Iran"s continued nuclear escalation means that we are rapidly reaching the end of the road," he said, flanked by the U.N. ambassadors from Britain and Germany, a group known as the E3. He added: "Iran"s nuclear program has never been more advanced than it is today. This nuclear escalation is undermining international peace and security and the global non-proliferation system." Under the 2015 accord, Iran limited its nuclear program - which the West feared would be used to develop weapons, something Tehran denies - in return for relief from U.S., European Union and U.N. sanctions. In 2018, then-U.S. President Donald Trump abandoned the deal and reimposed U.S. sanctions, prompting Iran to begin violating its nuclear restrictions about a year later. Indirect talks to salvage the deal are now underway in Vienna between Iran and the United States in which officials from the other nations shuttle between the two sides because Tehran rejects direct contact with U.S. officials.