Nuclear talks towards a lasting agreement between Iran and six powers appeared to make a progress on a second day Wednesday, with Washington saying the negotiations were "constructive and useful".

Nuclear talks towards a lasting agreement between Iran and six powers appeared to make a progress on a second day Wednesday, with Washington saying the negotiations were "constructive and useful".

Iranian state media said both sides were close to agreeing a framework agreement on how negotiations would proceed in future rounds over the coming months in what promises to be a lengthy process.

US State Department spokeswoman Marie Harf said that the Vienna talks between Iran and the United States, Russia, China, Britain, France and Germany had been "constructive and useful".

Negotiators discussed "both process and substance," she said.

Speaking to reporters, Harf declined to comment further, saying only that the talks would continue for a third day in the Austrian capital on Thursday.

Iranian Foreign Minister Mohammad Javad Zarif and EU foreign policy chief Catherine Ashton, the powers' chief negotiator, were expected to hold a closing news conference on Thursday morning.