Iran and international nuclear inspectors failed to agree on the start of an investigation into Iran's alleged nuclear weapons programme, dpa quoted a senior International Atomic Energy Agency (IAEA) official as saying Wednesday after talks between the two sides. "We must recognize that our best efforts have not been successful so far," IAEA chief nuclear inspector Herman Nackaerts said in Vienna after the tenth round of negotiations since early 2012. Iran's IAEA envoy Ali Asghar Soltanieh said the discussions on access to Iranian nuclear sites, documents and officials were "constructive and intensive." No date for a new round was agreed.