Family of father and son detained in Iran tells Trump to take 'urgent action': We're 'running out of time' Trump called on Iran to release all Americans during his U.N. speech.

 -- During his speech to the United Nations General Assembly, President Donald Trump called on Iran to release all Americans being detained by the regime and its Revolutionary Guard Corps.

Among those Americans held are a father and son -- Baquer and Siamak Namazi -- and their family is urging Trump to take "urgent action" to bring the two home.

Siamak Namazi was been held since October 2015. A Dubai-based businessman, he was detained while visiting relatives and sentenced for "cooperating with Iran's enemies." His father, Baquer Namazi, an 81-year-old retired UNICEF official, was detained in February 2016 as he worked to free his son; instead, he was tried and received the same guilty verdict.

Both are being held at the notorious Evin Prison, where they've faced solitary confinement and other harsh treatment.

Baquer Namazi was hospitalized Monday after the IRGC initially refused him medical services, according to the family's lawyer, Jared Genser. On Tuesday, Baquer Namazi underwent surgery to install a pacemaker, and on Wednesday, he'll be returned to prison, giving him little time to recover.

Sometime before Baquer Namazi was arrested, he had a triple bypass operation, but since he was imprisoned, he has lost more than 30 pounds and suffered from exhaustion, shortness of breath, dizziness and confusion, according to Genser.

"My family is rapidly running out of time," Babak Namazi, Baquer Namazi's son and Siamak Namazi's brother, said in a statement. "My father's health situation is dire, and I am horrified that he is being returned from a major surgery to recover in Evin Prison."

Babak Namazi and Genser have been quietly but intensely lobbying on Capitol Hill and with the administration to get the Namazis home, and Genser previously told ABC News the Trump administration has been very engaged and helpful.

The White House has placed a high priority on freeing Americans detained abroad, like Aya Hijazi who was released by Egypt and joined Trump in the Oval Office in April.

Now, Genser is asking Trump to do more -- thanking him for calling out Iran on the detentions, but saying, "This public engagement by the president must be followed by urgent action."

Among the options the family is asking the U.S. to look into is a prisoner swap. The Iranian regime may be interested in such an arrangement, according to Genser, citing an article by the pro-regime outlet Rajanews that named a handful of specific Iranian citizens whom the U.S. had charged with crimes and who are awaiting trial in America.

"I urge the president to spare no effort to bring my family home," Babak Namazi said, adding, that he hopes his father and brother won't suffer the same fate as Otto Warmbier, an American student who died earlier this year after being held by North Korea.

The White House released a statement in July saying it was "prepared to impose new and serious consequences on Iran unless all unjustly imprisoned American citizens are released and returned."

Just this week, the U.N. ruled that the Namazis were being detained illegally and must be released immediately and given compensation. Secretary-General Antonio Guterres has written to Iran's leaders demanding the two men's release as well, according to Foreign Policy.

The wife of Xiyue Wang, who is also being held by the Iranian regime, spoke out similarly last week, calling on the Trump administration to do more to "stand up for him."

Wang was detained in July 2016, but his detention was only recently revealed. A Ph.D. student studying history at Princeton University, he's accused of collaborating with foreign governments as well.

In addition to Wang and the Namazis, Iran has held Karan Vafadari and his wife, a green card holder, since July 2016 without filing charges and without giving them access to a lawyer, according to their family. The regime has also sentenced Reza Shahini to 18 years in prison, but released him on bond after he began a hunger strike. He remains in the country. And, American Bob Levinson went missing over 10 years ago in Iran. Iran denies that they have him in custody, but the White House has urged Iran to return him home.