Iran has given encouraging signs in recent days about opening informal talks with world powers and the United States, two European sources said on Thursday after European powers scrapped plans to criticize Tehran at the UN nuclear watchdog.Iran has so far refused to take part in a meeting brokered by the European Union between world powers and the United States on reviving its 2015 nuclear deal."Things are moving in the right direction, and we have had positive signals this week and especially in the last few days," a French diplomatic source said.The source added the objective was to get everyone around the table before the start of Nowruz, the Iranian New Year, on March 20, when Iran slows down administratively.He added that the window would also narrow from mid-April when Iran's presidential election campaign kicks in."We are putting all our efforts so that this (meeting) can take place in the days or coming weeks," the source said.A second European source also said there had been positive signals from the Iranian side. Diplomats said the obstacle for talks was that Iran was setting preconditions for attending to ensure that there would be a pathway to sanctions relief after the meeting, something the US could not accept."It's not a matter of giving an assurance of something that we'd do. It's sitting down and making sure that both sides do – as a first step, as a second step, whatever it is – that both sides are taking positive steps," a senior US official told Reuters on condition of anonymity."We can't tell them in advance what we're going to do if we don't know what they are going to do."An Iranian official declined to comment."Internal Iranian politics is causing constraints for the Iranian government which does not want to be at the same table as the Americans for the first time in years without being sure that it would lead at the end of this meeting to an effective process to lift sanctions," said the French diplomatic source.Iran's nuclear policy is decided by the country's top authority, supreme leader Ayatollah Ali Khamenei, and not the president or the government.Britain, France and Germany decided to pause the submission of a resolution critical of Iran at the International Atomic Energy Agency on Thursday to not harm the prospects for diplomacy and after what they said were concessions gained from Iran to deal with outstanding nuclear.