VIENNA - An Iranian envoy voiced hope on Monday that talks with the UN nuclear watchdog in mid-May would help resolve "outstanding issues", but he again ruled out any halt to Tehran's controversial uranium enrichment program.The International Atomic Energy Agency (IAEA) said on Saturday it would resume discussions with Iran on May 14-15 - more than two months after the last meeting over concerns about Tehran's atomic activities ended in failure.Envoy declines to comment on high-grade enrichment issueThe IAEA wants Iran to address the questions raised in the report. Iran has dismissed Western allegations as fabricated.Iran has also restarted negotiations with six world powers over the broader dimensions of its nuclear program and the sides have agreed to meet again in Baghdad on May 23.Iranian Foreign Minister Ali Akbar Salehi said last week that he was optimistic that the talks with United States, Russia, China, Germany, France and Britain would make progress.Washington and its allies believe Tehran is working on developing nuclear bombs. Tehran insists its activities have only civilian energy purposes and has refused to stop enriching uranium, despite a slew of sanctions."We (will) never stop enrichment activities in Iran," Soltanieh said, describing it as an inalienable right.He declined to comment however on Western demands that Iran halt the higher-grade enrichment, to a fissile concentration of 20 percent, it began in 2010 and has since sharply expanded, shortening the time needed for any nuclear weapons breakout.The UN Security Council has demanded that Iran suspend all enrichment activity but Western diplomats have indicated the immediate priority is to get it to halt the higher-grade work.Many analysts say it will only be possible to find a negotiated solution to the long-running row if both sides compromise: Iran would be allowed to continue some lower-level enrichment if it accepts more intrusive UN inspections."There is a growing recognition that zero enrichment is not a feasible solution," said Mark Fitzpatrick, a director of the International Institute for Strategic Studies think-tank."We hope that this will be a very constructive and successful meeting," Iran's ambassador to the Vienna-based IAEA, Ali Asghar Soltanieh, told Reuters."The main purpose is to negotiate on a modality and framework to resolve outstanding issues and remove ambiguities," he added, echoing language he and other Iranian officials have used before previous meetings that yielded no notable progress.He suggested that only after such a "framework" for future cooperation had been agreed could Iran consider an IAEA request for access to a military site where the UN agency believes nuclear-related weapons research may have taken place."Every action will be implemented based on this framework, afterward," Soltanieh said when asked whether the IAEA could visit Parchin southeast of the capital Tehran.Western diplomats have said Tehran still appeared to be stonewalling over the body's most pressing demand to let its inspectors visit the site.The IAEA last November issued a report detailing alleged Iranian research and development activities that were relevant to manufacturing nuclear weapons, lending independent weight to Western suspicions based on intelligence soundings.