Iran needs to reverse recent atomic activities that violate the 2015 landmark nuclear deal with world powers, Germanys Foreign Ministry said Friday as diplomats from the nations involved gathered in Vienna. The remaining signatories to the faltering Iran nuclear deal began crunch talks in Vienna Friday with questions over the survival of the landmark agreement after Tehran vowed to continue to breach the deals limits on its nuclear program. Envoys from Britain, France, Germany, China, Russia, and Iran are taking part in the meeting, which is the first time the six parties gather in this format since July. Iran has recently exceeded the stockpiles of uranium and heavy water allowed by the so-called Joint Comprehensive Plan of Action, and has started enriching uranium at a purity level beyond what is permitted. The JCPOA has been unraveling since the unilateral withdrawal of the United States last year and the re-imposition of American sanctions, which has left Irans economy struggling. Tehrans violations - all announced in advance - have been an attempt to put pressure on the other world powers involved - France, Germany, Britain, China, and Russia - to offer new economic incentives to offset the effect of the American sanctions. German Foreign Ministry spokesman Christofer Burger told reporters in Berlin, however, that the approach was "unacceptable" and that diplomats would make that clear at the Vienna meeting. "We will underscore that Iran must fully reverse its breaches of the JCPOA," he said. Since May, Iran has taken a series of measures, including stepping up uranium enrichment, in breach of the 2015 deal, with another such move likely in early January. Iran insists that under the agreement it has the right to take these measures in retaliation for the USs withdrawal from the deal in 2018 and reimposition of crippling sanctions. Since last month, European members have in turn begun raising the possibility of triggering the so-called "dispute resolution mechanism" foreseen in the accord, which could lead to the resumption of UN sanctions on Iran.