Iran's top negotiator in nuclear talks said on Thursday that he had insisted Tehran was serious in the negotiations, underlining that Iran was continuing discussions based on its previous positions.

"Iran underlined that it seriously continues the talks based on its previous position," Ali Bagheri Kani told reporters after talks resumed in Vienna. "Iran is serious about reaching an agreement if the ground is paved … The fact that all sides want the talks to continue shows that all parties want to narrow the gaps."

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The last round of talks aimed at reviving the 2015 Iran nuclear deal started November 29 and temporarily adjourned on December 3.

During the last talks, Iran submitted two draft proposals. But diplomats from Britain, France and Germany expressed "disappointment and concern" to the changes proposed by Tehran to the text negotiated during the previous six negotiating rounds, the last of which was held in June.

Wang Qun, Chinese envoy to the United Nations and other international organizations in Vienna last Friday, called on each party to inject new political impetus into the negotiations, although "a breakthrough is far from being achieved."

As the talks resumed in Vienna on Thursday, the coordinator of talks on the nuclear deal said he saw renewed will on all sides, including Iran, to reach an agreement, but that would now be tested as envoys go into details in the days ahead.

"What I felt this morning was from ... all delegations a renewed sense of purpose in the need to work and to reach an agreement on bringing the JCPOA back to life," the European Union's Enrique Mora told reporters after the remaining parties to the deal, the Joint Comprehensive Plan of Action, met.

(With input from agencies)