VIENNA  - The UN nuclear agency expressed confidence Friday that it will clinch a deal with Iran next month under which Tehran will at last answer “credible” evidence of atomic weapons research, but analysts and Western diplomats were sceptical. Returning from “good meetings” in Tehran on Thursday, International Atomic Energy Agency chief inspector Herman Nackaerts said that although Iran did not grant access to a key military base as he had hoped, he said this was “part of” the mooted accord. Such a breakthrough, if it really happens, could indicate that Iran, under massive sanctions pressure may give ground in parallel diplomatic efforts with six world powers stalled since June. But that is a big “if”, experts say.“We have agreed to meet again on 16 January next year, where we expect to finalise the structured approach and start implementing it then shortly after that,” Nackaerts told reporters at Vienna airport.Iran said that the meetings were “constructive, positive, and good progress has been made”. The IAEA wants Iran to address substantively a mass of what the agency calls “overall, credible” evidence set out in a major 2011 report that Iran did weapons research up until 2003, and possibly since then. Iran denies seeking or ever having sought nuclear weapons, and has rejected the alleged evidence outright in a string of previous fruitless meetings with the IAEA this year in Tehran and Vienna.This is because the bulk is from foreign intelligence agencies, including from arch-foe Israel, the Middle East’s sole if undeclared nuclear-armed state which has refused to rule out bombing Iran to stop it also getting the bomb.