American and Iranian negotiators met directly Tuesday to try to kick-start stalled talks meant to persuade Teheran to send most of its enriched uranium abroad - and thus delay its potential to make a nuclear weapon. The head of the UN nuclear agency said progress was slow but he expected a breakthrough. A diplomat at the closed-door talks told The Associated Press that a deal was "close" but not yet sealed. Foreign Minister Bernard Kouchner of France - one of the nations negotiating with Iran - warned that it and its partners in the talks "won't back down" on insisting that Teheran export most of its enriched material. Tuesday was the second day of talks in the Austrian capital between Iran and the United States, Russia and France over Iran's nuclear program. But the meeting convened only in the late evening after a day of backdoor negotiations, mediated in part by International Atomic Energy Agency chief Mohamed ElBaradei. Teheran says it needs enriched uranium for nuclear fuel but the US and other nations fear that could be used to make weapons. The US says Iran is one to six years away from being able to do so. Iran had signaled earlier that it might not meet Western demands for a deal under which it would ship most of its enriched material out of the country. Another problem appeared to be Iranian insistence that France be excluded from any participation in plans to turn the enriched material into fuel for Teheran's research reactor. While the main talks were stalled, the US, Russia, France and Iran staged separate meetings. Among these was an early evening encounter between the Iranian and American delegation "under the auspices" of ElBaradei, said Mike Hammer, spokesman for the US National Security Council. He gave no details on the substance of the talks. Iran and the US held their first direct talks in nearly three decades earlier this month in Geneva, where the five UN Security Council members and Germany met with Teheran to try to launch substantive negotiations meant to persuade Teheran to freeze its enrichment program. ElBaradei was cautiously upbeat with reporters shortly after the talks convened Tuesday. "We are making progress although slower than expected," he said. "But we are moving forward ... we hope to be able to reach an agreement." ElBaradei spoke of a "question of confidence building guarantees" - a possible allusion to the direct discussions between the Iranians and Americans and the need by both sides to defuse decades of distrust. As Tuesday's meeting ended, Ali Asghar Soltanieh, the chief Iranian delegate, said it "had been constructive. We will continue tomorrow." Iran, which holds a 10 percent share in a Eurodif nuclear plant in France, came to talks vociferously critical of French President Nicolas Sarkozy's government for withholding enriched uranium from that facility. Areva, the state-run French nuclear company, has described Iran as a "sleeping partner" in Eurodif, which Teheran bought into more than three decades ago. Iran is under three sets of UN Security Council sanctions for defying demands that it freeze uranium enrichment. The sanctions include embargoes on all shipments of sensitive nuclear materials or technology. In Teheran, Iranian Foreign Minister Manouchehr Mottaki downplayed the problem. "There are side issues ... with France," he told reporters. "We will talk about it when time is right." Earlier in the day, diplomats said discussion was focusing on a possible compromise that would involve Russia signing a deal with Iran to enrich the material and then "subcontracting" to France to turn it into fuel rods. That would formally meet Teheran's concerns that Paris not be directly involved. But the bigger challenge was persuading Iran to ship its enriched material out of the country. If Iran does what the West says it has already agreed to do, it would turn over more than 2,600 pounds (1,200 kilograms) of low-enriched uranium - as much as 75 percent of its declared stockpile. Tentative plans going into the meeting had been for further enrichment in Russia and then conversion in France into metal fuel rods for Iran's nuclear reactor. Kouchner indicated that Paris was ready to bow out of formal participation in the deal but would not compromise on insisting that Teheran ship out most of its enriched material. If Iran accepts, "it must be before the end of the year, there must be at least 1,200 kilograms - on that we won't back down," Kouchner told reporters in Paris. Iran agreeing to ship most of its enriched uranium abroad would significantly ease fears about Teheran's nuclear program, since 1,000 kilograms is the commonly accepted amount of low-enriched uranium needed to produce weapons-grade uranium. Based on the present Iranian stockpile, the US has estimated that Teheran could produce a nuclear weapon between 2010 and 2015, an assessment that broadly matches those from Israel and other nations. David Albright of the Washington-based Institute for Science and International Security, which has tracked Iran for signs of covert proliferation, said any such deal would buy only a limited amount of time. He said Teheran could replace 1,200 kilograms of low-enriched uranium "in little over a year."