Iran’s foreign minister has said he is positive about the prospects of a long-term agreement with the international community on its nuclear programme, following talks with the six major international powers in Austria.

Mohammad Jayad Zarif was quoted by the Iranian Fars news agency as saying he saw “signs” of a nuclear deal with international states, and that “an understanding is possible that respects the rights of the Iranian nation”.

The comments from Zarif followed a statement he had made with EU foreign policy chief, Catherine Ashton, that the talks between Iran and six world powers in Vienna on 18 March were “substantive”.

The talks are part of efforts to build on an interim deal signed in November 2013, under which Tehran agreed to limit uranium enrichment in return for an ease of international sanctions.The deal, which was negotiated in Geneva, represented a major breakthrough after years of political tension between Iran and the West. The United Nations’ nuclear watchdog, the International Atomic Energy Agency (IAEA), is overseeing the enforcement of the agreement. The interim agreement began on 20 January, and will be enforced for six months.

The sides are due to meet in Vienna again on 7-9 April to continue negotiations, and Zarif said he was “optimistic” about meeting the 20 July deadline for a long-term deal.

The six major powers, the US, UK, France, China and Russia plus Germany, are seeking to bind Iran to an agreement to permanently curb its nuclear activities, to ensure that it does not have capabilities to build nuclear weapons. Iran insists that its nuclear development is solely for power production.

Iran’s diplomatic relations with the US and other world powers have opened up significantly since Hassan Rouhani took over as Iranian president in August 2013.