US pushing Iran to return elderly American prisoner said to be in failing health

— -- The U.S. is pushing behind the scenes with Iran to return an elderly American held by the regime — after the 81-year old man was granted a four-day leave from an Iranian prison, according to his family and a senior State Department official.

Baquer Namazi, a retired United Nations official who has been held by Iran since 2016, was rushed to the hospital less than two weeks ago after a severe drop in his blood pressure and irregular heartbeat among other symptoms, his family said then. He has now been released and put on leave for four days, unable to speak to the media or leave Iran.

But his family — and the Trump administration — are using this reprieve to push for his return to the U.S. for medical treatment.

The family says Namazi’s doctors have strongly advised against his return to Evin Prison saying that the prison conditions are “dangerous” for him and would rapidly exacerbate his ailing health.

A senior State Department official tells ABC News that the U.S. is using back channel communications, especially through European allies, to push for his return over the next four days — before his scheduled return to Evin prison on Feb. 1.

Under Secretary of State for Political Affairs Tom Shannon raised the issue directly with Iran at a meeting on the Iran nuclear deal in Vienna, Austria, last month, the official said.

In particular, the official said, they are sending signals to Iran warning, “They don’t want a case similar to Otto Warmbier’s on their hands.”

"If Namazi goes back to this notorious prison," the official said, "he may not live much longer, given how much his health has deteriorated."

Otto Warmbier, a 22-year-old American college student held by North Korea for 17 months, died six days after being returned to the U.S. last June.

Both Baquer Namazi and his son Siamak, who has been imprisoned since 2015, are serving 10-year sentences for what Iran says is “cooperating with Iran’s enemies.”

Babak Namazi, another son of the elderly American in Iran, called for authorities to show compassion:

“While I am grateful the Iranian Government has granted a four day leave for my father, a return to prison would be life threatening for him. My father is in very poor health and has been hospitalized four times. I beg the Iranian authorities to show compassion and grant my father a permanent release so he can spend his remaining time with his family before we face an irreversible tragedy.”