Iran's chief nuclear negotiator Abbas Araghchi says negotiations in Vienna over reviving the 2015 Iran nuclear deal have been "moving ahead slowly."

Speaking to reporters at the end of Saturday's session of the negotiations he said, "The pace of the negotiations has slowed down as we have started to write texts in some areas." However, he did not elaborate.

A reporter asked: "The Americans have said they will lift some of the sanctions, do you agree with that stance?" Araghchi answered: "We would not need to negotiate if the two sides agreed with each other's stances. The negotiations are about the differences in views."

However, Araghchi added that "we will continue to negotiate until the wo sides' positions come close to one other." He continue that "There is more mutual understanding  about lifting sanctions  in various areas than sanctions on individuals."

He did not name any individual but Iran's Supreme Leader Ali Khamenei is one of the individuals who has been sanctioned by the United States under the Trump Administration.

Araghchi named "some of the subjects and sectors under sanctions including the energy sector, the automobile industries, as well as insurance, and banking, stressing that talks about these subjects still continue, however, agreement has been made on most of them, but there are still others that should be discussed later."

Summing up the outcome of negotiations, he said: "Now we understand the differences more accurately and clearly." However, he added: "We still do not know when and how we are going to reach an agreement."

Delegates in the Vienna talks left for their countries Saturday afternoon and the next meeting will be on Friday, May 7.

Although Araghchi's cautiously optimistic statement was clear enough, some Western sources and reporters appeared even more optimistic Saturday evening.

According to Reuters, Russia and Western European powers gave contrasting accounts of the task ahead in the talks to bring Iran and the United States fully back into compliance with the 2015 nuclear deal, as the talks adjourned for six days.

Earlier, Reuters had quoted European sources as having said that "the toughest issues are still unresolved in the Iran talks.”

Saturday's talks were the third round of indirect negotiations between Iran and the United States aiming at both countries returning to their obligations under and compliance with the full terms of the 2015 nuclear accord between Iran and world powers also called the Joint Comprehensive Plan of Action (JCPOA).

The United States which was a key player in the P5+1 that forged the deal with Iran, left the accord in 2018 under President Donald Trump. Iran waited for a year for America to return to the deal and in the meantime called on Europe to make up for Tehran's losses. Iran said the JCPOA's European partners did very little to help Iran, so from May 2009 Iran gradually started to reduce its obligations under the accord by producing more higher grade enriched Uranium and installed modern centrifuges in its nuclear facility in Natanz to further boost enrichment.

President Joe Biden promised before the 2020 US Presidential election to return to its obligations under the JCPOA. Later, the US side said that Iran should return to full compliance of the deal before the United States lifted some of the sanctions on Iran.

The Iranian side has officially announced that it demands the lifting of all of the US sanctions in a way that would be verifiable for Tehran. The US called this "unacceptable."