Tehran, Dec 13 : The US must lift the sanctions it has imposed on Iran in exchange for its return to the 2015 nuclear agreement, Tehran's chief negotiator said. One of the main goals of the Vienna talks was "to establish the conditions that the Americans must meet," Ali Bagheri Kani, also Iran's Deputy Foreign Minister, told the media in Vienna where the seventh round of negotiations aimed at implementing the deal is underway. Once those conditions are agreed upon, the Americans will have the duty to implement them, and the core requirement is the lifting of "the iniquitous and illegal sanctions", Xinhua news agency quoted the chief negotiator as saying. The positions of the parties in the talks are different on different issues, but during the last days the extension of the subjects open to the discussion has been reduced, Bagheri Kani noted. Speaking of the "non-constructive comments" from three European parties to the talks, the Iranian chief negotiator said he was optimistic about the future of the negotiations. However, the "hostile, illegal, destructive and even inhumane acts by some parties", as well as the existing mistrust, do not allow for any naivety concerning the process ahead, he added. The ongoing talks on the 2015 Joint Comprehensive Plan of Action (JCPOA) is being negotiated by EU officials and China, France, Germany, Russia, the US and Iran. The goal of the JCPOA is to restore the 2015 nuclear agreement, which the US withdrew from in 2018 under the administration of former President Donald Trump, unilaterally re-imposing sanctions on Iran. Tehran has retaliated by gradually stopping implementing elements of the deal since May 2019. The seventh round of talks started on November 29, lasting for five days, during which Iran submitted draft proposals for a restored 2015 nuclear agreement. However, senior diplomats from the UK, France and Germany on December 3 voiced "disappointment and concern after thoroughly and carefully analysing Iranian proposed changes to the text negotiated during the previous six rounds". /IANS