Officials representing Iran and the so-called P5+1 group of world powers are scheduled to hold talks later on Wednesday in preparation for a senior-level meeting due on March 17, aimed at reaching a comprehensive and final accord on Iran's nuclear file.Sources of the International Atomic Energy Agency (IAEA) said the scheduled three days of preparatory talks, due to begin later today, would focus on Iran's controversial issue of uranium enrichment and tackling file of Arak heavy-water reactor, feared by the West as potentially capable of developing military nuclear arms.Officials from the two sides have generally voiced satisfaction at outcomes of previous rounds of negotiations, although the IAEA chief, Yukia Amano, says some pending issues in the Iranian nuclear file remain to be resolved.Moreover, Amano has demanded that Tehran clarify issues "related to the suspected aspects of its nuclear program" and implement the inspection protocol.Speaking at a news conference late on Monday, Amano voiced satisfaction at Iran's implementation of measures related to its nuclear program but called for greater efforts to resolve relevant pending matters.Iran has carried out "the six practical procedures," included in the cooperation treaty with the International Atomic Energy Agency (IAEA), he said.The IAEA had agreed with Iran regarding execution of up to seven measures, to be accomplished by May 15, he added, adding that the agency started examination of the joint action plan that had been drawn up in coordination between Iran and the P5+1 states Amano was alluding to sufficient progress on Iran's part regarding implementation of the six-month accord in tackling its nuclear program in exchange for some easing of sanctions that have impaired its oil-dependent economy.The measures stipulated in the treaty include dilution of a proportion of Iran's inventory" of 20 percent uranium gas to a lower enrichment level.Amano affirmed that the measures that had been undertaken by Tehran at this level were positive, but "still more work should be done regarding the Iranian nuclear program." The powers involved in the marathon on-and-off talks with Iran are the UN Security Council members Britain, China, France, Russia and the United States, plus Germany.The IAEA said last month that uranium enrichment to medium levels -- the main concern to the international community -- "is no longer taking place", as agreed in the November deal.The IAEA also said that a proportion of Iran's medium-enriched uranium stockpile "is being down-blended, and the remainder is being converted to uranium oxide".