TEHRAN – Nuclear negotiators who have gathered in Vienna after a five month-hiatus have indicated that they are optimistic about reviving the 2015 nuclear deal, officially known as the Joint Comprehensive Plan of Action (JCPOA).

“We stand five minutes or five seconds from the finish line,” Russian Ambassador Mikhail Ulyanov told reporters outside Vienna’s Palais Coburg on Sunday, four days into the talks. He said there are “three or four issues” left to be resolved.

“They are sensitive, especially for Iranians and Americans,” Ulyanov said. “I cannot guarantee, but the impression is that we are moving in the right direction.”

Enrique Mora, the European Union’s top negotiator who acts as mediator between Iran and the U.S., also said he is “absolutely” optimistic about the talks’ progress so far.

“We are advancing and I expect we will close the negotiations soon,” he told Iranian media.

The Wall Street Journal also said negotiations between Iran and the U.S. on reviving the JCPOA are close to completion, Mora said on Sunday evening.

The text of an agreement could be closed in coming hours, said Mora.

According to the Iranian diplomats, experts are focusing on technical issues about Iran’s nuclear program.

Behrouz Kamalvandi, the spokesman for the Atomic Energy Organization of Iran (AEOI), confirmed on Saturday that the talks are mainly focused on Safeguards issues.

One of Iran’s demands is that the IAEA should stop unsubstantiated allegations regarding PMD that had already been resolved in July 2015, when the nuclear deal was struck.

In a telephone call with UN Secretary General Antonio Guterres on Sunday afternoon, Iran’s Foreign Minister Hossein Amir-Abdollahian said, “We believe that the Agency should completely resolve the remaining issues related to the Safeguards [Agreement] by distancing itself from irrelevant and nonconstructive political issues and through the technical channel.”

He added, “Nuclear weapons have no place in the [defense] doctrine of the Islamic Republic of Iran and are in contradiction to our policies and beliefs,” referring to a fatwa (religious decree) by Leader of the Islamic Revolution Ayatollah Seyyed Ali Khamenei declaring that the production, stockpile and use of nuclear weapons as forbidden.

"The Leader's fatwa that prohibits the use of nuclear weapons is clear-cut and is the final say for everybody," Iran's foreign minister said.