Sullivan said a critical early priority for the Biden administration is to address what he called an escalating crisis with Iran.
"From our perspective, a critical early priority has to be to deal with what is an escalating nuclear crisis as they (Iran) move closer and closer to having enough fissile material for a nuclear weapon," Sullivan told an online program sponsored by the US Institute of Peace, Reuters reported.
“We would like to make sure that we reestablish some of the parameters and constraints around the [Iran’s nuclear] program that have fallen away over the course of the past two years,” He added according to the Washington Post.
Iran’s Leader Ayatollah Seyyed Ali Khamenei has issued a fatwa (religious decree) prohibiting the production of nuclear weapons.
The timing of a US return to the deal, as well as new concessions or promises made to Iran and the scope of a potential follow-on agreement, is one of the first major foreign policy tests for the Biden administration.
The 2015 nuclear deal has been raveling since former US president Donald Trump pulled his country out of the accord in 2018 and reinstated and reinforced tough sanctions on Iran.
The US pullout came as US nuclear watchdog confirmed Iran’s compliance with in more than 10 reports.
Trump’s withdrawal sparked strong opposition from other parties to the deal – the UK, France, Germany, China and Russia.
A year later, Iran began to roll back most parts of its nuclear work it response to US exit.
Biden has promised to return to the accord and seek diplomacy with Iran.
Iranian officials have said what matters to the country is the lifting of all US sanctions. They have also ruled out a renegotiation of the deal.