Iran's foreign minister said on Saturday that the United States had an obligation to help revive Tehran's 2015 nuclear deal with world powers which Washington had abandoned, after President Joe Biden said it was unclear how serious Tehran was about talks on the accord.
The United States has expressed its readiness to lift many of its sanctions on Iran at the Vienna nuclear talks but Tehran is demanding more, Iran's senior negotiator said on Friday.
Biden said he believed Iran was seriously engaging in the talks but it was unclear what Tehran was actually prepared to do to resume compliance with the deal.
Asked if he thought Tehran was serious about talks, Biden replied: "Yes, but how serious, and what they are prepared to do is a different story."
US officials are holding indirect talks with Iran in Vienna on how to resume compliance with the deal, which former President Donald Trump abandoned in 2018.
"As we try to revive JCPOA (nuclear agreement) in Vienna, it's necessary to remember how it all started. 3 years ago today, a disgraced buffoon violated US obligations...," Iranian Foreign Minister Mohammad Javad Zarif said on Twitter.
"Today, @POTUS (Biden) has to decide whether US continues lawlessness or adheres to law. Onus is on US, not Iran," Zarif said.
Trump's withdrawal from the accord prompted Iran a year later to begin violating the terms of the agreement that aimed to rein in Tehran's nuclear ambitions in return for the lifting of sanctions. Tehran denies seeking nuclear weapons.