The 84-year-old father of America’s longest-serving hostage in Iran has been stopped from leaving the country despite his own 10-year jail term being cut short because of his dire medical condition, his family revealed on Monday. Baquer Namazi, a US-Iranian dual national, was jailed in 2016 after flying to Iran to visit his son Siamak who was detained the previous year and subsequently convicted of collaborating with the US. Baquer, a former Unicef official, was released on medical grounds in 2018 and his family disclosed for the first time on Monday - the fifth anniversary of his arrest – that his sentence was commuted in February 2020 and he was told he could prepare to leave the country. But the Islamic Revolutionary Guard Corps blocked the ailing Mr Namazi from securing a new passport that would allow him to leave to secure vital medical help. The main artery to his brain is 80 per cent blocked and he is at high risk of suffering a stroke, his family said. Mr Namazi has been told he should have the surgery in a stress-free environment outside of Iran where he can have a long-term plan for recovery. “My father will not last much longer,” said his son Babak Namazi, who has campaigned for the release of both his brother and father. He said it was not clear why his father’s departure was being blocked. “What other reason could there be other than torment? “It was a shock to me that Iran takes that step of commuting his sentence. I thought they have seen the logic of letting this man go and then made the situation worse by not allowing him to leave.” He said that his brother Siamak, a Dubai-based businessman, was “beyond despair” and had learned of the release of other western hostages, including Americans, while he languished in a cell at Evin prison. “My family will not survive being left behind again,” said Mr Namazi. Iran has arrested dozens of dual nationals in recent years, mostly on espionage charges. They have been used as bargaining chips as part of a broader diplomatic power struggle and to secure the release of Iranian prisoners abroad. Prisoners from the US, France, Germany, Austria, Sweden and the UK continue to be held by Iran on what governments and supporters say are trumped-up charges. “In essence, they take hostages like picking stock,” said the Namazis’ lawyer, Jared Genser. “Sometimes they go up, and sometimes down, and they are prepared to trade them when they have value.” Mr Genser last week argued that Iran must release all dual nationals before US President Joe Biden’s administration agrees to lift sanctions or enter negotiations with Tehran. The US said last week that it was ready to talk to Iran about returning to the 2015 nuclear accord, abandoned by former president Donald Trump's administration. The accord aims to stop Tehran acquiring nuclear weapons, while lifting most international sanctions. "This would clearly demonstrate that Washington won't tolerate hostage-taking as a foreign policy tool," Mr Genser wrote in the <em>Wall Street Journal</em>. "It would be especially powerful if this position were taken in conjunction with other countries whose citizens Iran has taken hostage in recent years." White House National Security Adviser Jake Sullivan said on Sunday that the US had begun to communicate with Tehran over its detention of American nationals. Mr Sullivan said the matter was a “complete and utter outrage” and a “humanitarian catastrophe”. Human rights activists accuse Tehran of trying to use the detentions to win concessions from other countries, a charge it denies. It was a “significant priority” of Mr Biden’s administration to bring those Americans “safely back home”, Mr Sullivan told CBS. “We have begun to communicate with the Iranians on this issue,” he said. “We will not accept a long-term proposition where they continue to hold Americans in an unjust and unlawful manner.” Elliott Abrams, the US special representative for Iran under Mr Trump, told <em>The National</em> in November that it would be "unconscionable" for any US president to make a new deal with Iran that didn't include the release and return of western hostages. Mr Sullivan said Mr Biden was “determined” to prevent Iran from obtaining a nuclear weapon and diplomacy was the best way to achieve that. The two countries have been at odds over which should take the first step to revive the deal. Iran’s foreign ministry said on Sunday that the US should not be allowed to re-join the nuclear pact until it lifted sanctions, but Washington said Tehran must first return to compliance. The EU is looking to broker a meeting between Washington, Tehran and other signatories in an attempt to salvage the accord from which Mr Trump withdrew the US in 2018. European Union foreign ministers are meeting in Brussels on Monday for talks that included a video conference with new US Secretary of State Antony Blinken. Mr Blinken spoke with relatives of detained Americans within days of taking on the job and expressed his commitment to securing their release.