The number of candidates contending to be the Democratic Party’s nominee to take on US President Donald J. Trump in next year’s elections have grown with each passing week.

In an effort to highlight their differences with Trump, four of the Democratic hopefuls – Bernie Sanders, Elizabeth Warren, Kamala Harris, and Wayne Messam – said they are committed to rejoining the 2015 Iran nuclear deal that Trump pulled out of after Tehran refused to dial-down their aggressive foreign policy initiatives in the Middle East.

Former Vice President Joe Biden, who is expected to announce his own bid for the nomination, is also committed to the Iran deal.

A group of former Barack Obama administration officials has circulated a draft memo to all declared Democratic candidates asking them to rejoin the Joint Comprehensive Plan of Action or JCPOA, Al-Monitor reports.

“While we won’t speak to private conversations, the message we have been sending is clear and simple,” said Ned Price, the group’s policy director. “If Iran remains in compliance, the next administration should rejoin the Iran deal and use principled diplomacy to negotiate a follow-on agreement to keep the Iranian nuclear program in a box for the long term.”

The US Office of the Director of National Intelligence and the International Atomic Energy Agency have often confirmed that Iran remains in compliance of the 2015 agreement.

Iran is due to hold its own elections in 2021. Concessions by a US administration could tilt the balance of power domestically as moderates in Iran have been under criticism by hardliners since Trump pulled out of the deal.