(Adds quotes on 20 percent fuel production and Fordow)
ALMATY, Feb 27 (Reuters) - Iran said nuclear talks with world powers were a "positive step", after two days of negotiations that ended in Almaty on Wednesday.
In a statement, Iran said expert level talks between the two sides would be held in Istanbul on March 18, and another round of political negotiations on April 5-6.
Iran's chief nuclear negotiator suggested Iran could discuss its production of nuclear fuel enriched to a fissile concentration of 20 percent - which greatly worries the West - but appeared to rule out closing the underground Fordow enrichment plant where that takes place, which the powers demand.
In comments in Persian translated into English, Saeed Jalili told a news conference Fordow was under the supervision of the U.N. nuclear agency and there was "no justification" to shut it down.
Asked about the production of 20 percent enriched fuel - a relatively short technical step away from weapons-grade material - he reiterated Iran's position that it needed this for a research reactor and had a right to produce it.
But Jalili indicated that Iran may be prepared to discuss the issue: "This can be discussed in the negotiations ... in a view of confidence building."
Iran has also previously suggested that 20 percent enrichment was up for negotiations if it received the fuel from abroad instead. It also wants sanctions lifted.
Jalili said the six powers - the United States, France, Germany, Britain, Russia and China - at Almaty had tried to "get closer to our viewpoint", which he said was positive.
The Iranian statement said: "We consider these talks a positive step which could be completed by taking a positive and constructive approach and taking reciprocal steps." (Reporting by Yeganeh Torbati Justyna Pawlak, Fredrik Dahl; Editing by Kevin Liffey)