A member of the Iranian parliament said on Sunday although Tehran and other parties to the 2015 nuclear deal have prepared the main draft of a possible agreement, they still have differences on a few unresolved issues in the Vienna talks.

Abolfazl Amouei, a member of the Iranian parliament's National Security and Foreign Policy Committee, said that Tehran will only sign an agreement if these issues are solved, according to the semi-official Tasnim news agency.

The first issue is pertinent to the measures the United States is needed to take in a bid to regain its former status as a party to the nuclear deal, officially known as the Joint Comprehensive Plan of Action (JCPOA), the lawmaker said.

To that end, lifting the sanctions on Iran and providing it with the opportunity of having international interactions and cooperation are Tehran's fundamental requests based on the JCPOA, he added.

Amouei noted that concerns about U.S. fulfillment of its commitments are currently beyond worries voiced by Iran, and have become an international issue.

"Different countries are worried if the United States would fulfill its commitments under the JCPOA if the deal is restored," he said.

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Iran says Vienna nuclear talks in 'final critical steps'

Iran and the remaining parties to the JCPOA are currently involved in negotiations in Vienna seeking to settle disputes on the revival of the nuclear pact.

Iran signed the JCPOA with world powers in July 2015. However, former U.S. President Donald Trump pulled Washington out of the accord in May 2018 and reimposed unilateral sanctions on Iran, which prompted the latter to drop some of its nuclear commitments one year later and advance its halted nuclear program.