Negotiators for Iran and six world powers will adjourn their talks on reviving their 2015 nuclear deal on Sunday and return to respective capitals for consultations as remaining differences cannot be easily overcome, Iran's delegation chief said. 

"We are now closer than ever to an agreement but the distance that exists between us and an agreement remains and bridging it is not an easy job," Abbas Araqchi, Iran's envoy and deputy foreign minister, told Iranian state TV from Vienna. "We will return to Tehran tonight." 

Since April, negotiations have been going on in Vienna to iron out steps Iran and the United States must take on nuclear activities and sanctions to return to full compliance with the nuclear pact, officially known as the Joint Comprehensive Plan of Action (JCPOA). 

Washington withdrew from the deal in 2018 and reimposed sanctions on Tehran. In response, Iran gradually stopped implementing parts of its JCPOA commitments from May 2019. 

Sunday's meeting, the sixth round of talks in the Austrian capital, took place a day after Ebrahim Raisi, a hardliner, won the presidential election in Iran. Negotiators have said the election is not expected to influence the talks, though Raisi's views are widely seen as a break from the more moderate stances of outgoing President Hassan Rouhani.

"Bridging the gaps requires decisions that mainly the other party (Washington) has to take. I hope in the next round we will travel this short distance – albeit a difficult one," Araqchi said. 

U.S. national security adviser Jake Sullivan said on Sunday that there are still disagreements between Iran and the world powers, reiterating that the ultimate decision on the issue lies with Iranian Supreme Leader Ayatollah Ali Khamenei. 

"There is still a fair distance to travel on some of the key issues, including on sanctions and on the nuclear commitments that Iran has to make," Sullivan said in an interview with broadcaster ABC News, adding that the question of which sanctions on Iran were to be lifted was still being discussed. 

Mikhail Ulyanov, the Russian envoy at the EU-chaired talks, said Sunday's meeting would "decide on the way ahead."  

"An agreement on restoration of the nuclear deal is within reach but is not finalized yet," he wrote on Twitter on Saturday. 

China has stressed that in order to resume full compliance with the JCPOA, the U.S. should first lift its unilateral sanctions against Iran, including "long-arm jurisdiction" against third-party entities and individuals. 

Iran's arch-enemy, Israel, on Sunday condemned Raisi's election. In a televised statement at the start of the government meeting, Israeli Prime Minister Naftali Bennett said Raisi's victory is a "final wake-up call" for the world powers not to renew the nuclear deal. 

Like his predecessor Benjamin Netanyahu, Bennett is an opponent of the renewal of the nuclear deal between the world powers and Iran. 

(With input from agencies)

(Cover: Iranian Deputy Foreign Minister Abbas Araqchi (R) and EU negotiator Enrique Mora attend the JCPOA meeting in Vienna, Austria, June 12, 2021. /Getty)