The family of two Iranian-Americans held in Iran is urging the Biden administration to make the release of hostages a key part of its Iran policy and to ensure that they are not left behind again.

Babak Namazi, the son of Baquer and brother of Siamak Namazi, told reporters Monday that it "pains (him) greatly that we are now in into a third administration, with both (his) brother and father still being held captive."

"As the Biden administration develops its new Iran policy, my family expects that President Biden and his administration will not make concessions or deals with Iran that do not include, and indeed require as a precondition, the release of my father and Siamak," Babak said. "Their releases should not be a subsequent step. That approach by both the Obama and Trump administrations failed."

Siamak was blocked from leaving Iran after visiting in July 2015 and underwent months of interrogations before being arrested in October 2015. Exactly five years ago, his father, Baquer, was lured to Iran under the false premise that he would be able to see his son. He was instead immediately taken into custody at that time.

Babak revealed for the first time Monday that his father's sentence had been commuted, but he has still been barred from leaving Iran. He is deeply concerned for his elderly father, particularly amid the country's Covid crisis.

"My father will not last much longer under such conditions, and the Covid outbreak in Iran compounds greatly the ongoing dangers my father faces," Babak said, adding, "my family will not survive being left behind yet again."

Baquer was released on temporary medical furlough in February 2018, and in February 2020 Iran's Revolutionary Court commuted Baquer's sentence to time served and the travel ban on him was lifted.

"At the time, as you can imagine we were overjoyed privately that finally the nightmare may be over for my father, and he can leave Iran to get the much-needed medical attention and procedures he needs, and to spend what little time he has left with his grandchildren," Babak explained.

However, "inexplicably" in May 2020, the family was informed that Iran's Islamic Revolutionary Guard Corps (IRGC) had placed a new travel ban on Baquer, preventing him from leaving the country.

"I urge the government of Iran to stop playing with my father's life, and allow him to depart Iran immediately. There exists no legal basis or justification for preventing my 84-year-old frail father from leaving, even under Iranian law. My father has been requiring immediate medical attention for quite some time," Babak said.

Although he is able to speak to his father by video now that he is out of prison, Babak said Baquer and Siamak have missed out on innumerable moments with his family. Babak said he is able to speak with Siamak "regularly," but sometimes it is hard to convey hope to his brother.

"He is constantly in fear that he's going to be left behind. He's constantly in fear that no one is thinking about it. He's constantly in fear that he doesn't matter," Babak said.

Other Americans being held

In addition to the Namazis, Americans Morad Tahbaz and Emad Sharghi are publicly known to be held in Iran. Bob Levinson, an American who was abducted in Iran in 2007, is believed to have died in Iranian custody.

On Sunday, US national security adviser Jake Sullivan told CBS News that the administration "(intends) to very directly communicate with the Iranians about the complete and utter outrage, the humanitarian catastrophe that is the unjust, unlawful detention of American citizens in Iran."

"We have begun to communicate with the Iranians on this issue, yes. And we will continue to do so as we go forward. And our strong message to the Iranians will be that it -- we will not accept a long-term proposition where they continue to hold Americans in an unjust and unlawful manner," Sullivan said.

The Iranian government rejected Sullivan's claim and said that communications on the matter were being held via the Swiss, the US protecting power in Iran, according to Iran's Supreme National Security Council's news website, Nournews.

On Monday, White House press secretary Jen Psaki said, "We have a range of means of communicating with the Iranians and we've certainly raised American citizens who are being held in Iran through those channels, but I don't have anything more specific."

The comments came days after the administration said it would be willing to sit down to multilateral talks with Iran, the EU and the P5+1 -- the permanent members of the UN Security Council and Germany.

The US would be represented at those talks by special envoy Rob Malley. The Namazi's legal counsel, Jared Genser, said Monday he has spoken to Malley.

"He assured me, much as the Secretary assured Babak, that the release of American hostages will be a top priority. We didn't discuss the precise ways that it would be raised, and what precise formats; we were just told unequivocally that that it would be a top priority," Genser said.

He said the fact that the Biden administration has already reached out and asked for discussions on the matter is "about the best that one can hope for at this stage."