Both the United States and Iran said Wednesday that talks to revive the 2015 nuclear deal are in their final stages, while hedging their bets about the outcome.

State Department spokesperson Ned Price said on Wednesday that the US is in "the midst of the very final stages" of indirect talks with Iran.

"This is really the decisive period during which we'll be able to determine whether a mutual return to compliance with the JCPOA is in the offing, or if it's not."

China's chief negotiator in Vienna, Wang Qun, also told Iran International's correspondent that the next day or two can be decisive in the talks, which are in their final satge.

Iran's top nuclear negotiator, Ali Bagheri Kani said on Twitter on Wednesday that "after weeks of intensive talks, we are closer than ever to an agreement; nothing is agreed until everything is agreed, though."

Iran’s foreign minister Hossein Amir-Abdollahian in an interview with the Financial Times said that any guarantee of a lasting agreement by the Biden Administration would not be enough and Tehran wants an assurance from Congress. Iran has been insisting to receive a guarantee that the US will not withdraw from a deal again, as former President Donald Trump decided to abandon the JCPOA in 2018.

Republicans and some Democrats have serious reservations about President Joe Biden’s Iran policy of reviving the JCPOA.