Elliott Abrams is a senior fellow for Middle Eastern studies at the Council on Foreign Relations in Washington.

Many issues relating to Iran are complicated, but one is very simple: Iran keeps taking American hostages. The Biden administration must secure their releases. And it shouldn’t stop there: It should also take action to end hostage-taking by the regime in Tehran. Not one sanction on Iran should be lifted until this has been achieved.

Iran’s practice of taking American hostages began in 1979 when the U.S. Embassy was overrun. It has never stopped but, now, the regime is focusing on those with dual citizenship. As the Biden administration came into office, it was greeted with the unjust conviction and jailing of a fourth American. As NBC reported on Jan. 17, Emad Shargi, 56, was told on Nov. 30 that he had been convicted of espionage without a trial and sentenced to 10 years. Shargi’s family has not heard from him for more than six weeks.

The three other Americans now unjustly detained are Morad Tahbaz and Baquer and Siamak Namazi, who are father and son. Tahbaz is a co-founder of the Persian Wildlife Heritage Foundation. Baquer Namazi is a former UNICEF official who is 84 years old. When Siamak Namazi, an American businessman, was imprisoned in 2015, Baquer flew to Iran to try to argue for his son’s release. Instead, he, too, was imprisoned. He is now under house arrest — but the ayatollahs will not let this elderly man leave the country and be united with his family for however many years he has remaining.

Last year, as U.S. special representative for Iran, I had the honor of meeting with members of Morad Tahbaz’s family at the State Department, and then with Siamak’s brother Babak in Abu Dhabi. Such meetings with hostage families are always emotional, but Babak had a special story to tell: The Obama administration and Iran’s foreign minister, Javad Zarif, had promised Baquer Namazi’s release. John F. Kerry, the secretary of state, had personally promised it.

The dates tell a remarkable story: Siamak was arrested in October 2015, Baquer in February 2016. These two events fell during the period when the nuclear deal, the Joint Comprehensive Plan of Action, was coming into being. The agreement was reached on July 14, 2015, “Adoption Day” was Oct. 18, 2015, and “Implementation Day” was Jan. 16, 2016. Obviously, Iran felt absolutely free to proceed with these unjust arrests and convictions despite the JCPOA negotiations — and the U.S. government allowed it to happen. That is to say, there was zero linkage.

But there must be linkage: The U.S. government must never put negotiations with hostile regimes above the safety of its citizens, and must not allow such regimes to treat them as pawns. When we do, as in the case of Iran, we guarantee that more Americans will be arrested.

One of the two Iranian hostages freed in recent years was the Princeton student Xiyue Wang, who spent 40 months in Evin Prison. In several interviews since his release, he has been asked about how he was questioned. The assumption was that the questioning was very harsh, but Wang says it was not — because the interrogators understood fully that he was not a spy, had no information for them and was simply a hostage. So what is to be done? Here is Wang’s view:

“The U.S., the European Union, Britain, Canada and Australia . . . should require the regime, as a precondition for any future political deal, to release all hostages and forswear hostage-taking in future. Nobody else should have to experience the ordeal I endured.”

Post journalist and former hostage Jason Rezaian, released in January 2016, recently made the same point:

"Biden should take a clear stand — along with Germany, France and Britain — that there will be no new negotiations until nationals of these countries and other allies held hostage in Iran are set free and the Islamic republic commits to quitting this savage practice.”

This is not special pleading but a point of principle the Biden administration should adopt immediately. In asking the excellent special presidential envoy for hostage affairs, Roger Carstens, to stay on from the Trump administration into the Biden administration, the first step was taken. But Carstens will not set policy toward Iran, and the resolve to end hostage-taking can only come from the president and secretary of state. The time to make the decision is right now, as the administration comes into office.

The “savage practice” must be ended and the American hostages released. There should be no relief from U.S. sanctions on Iran — none whatsoever — until the hostages are freed. Whatever one’s view of the nuclear deal, or U.S.-Iran relations (Wang and Rezaian have very different views), this proposition should unite all Americans.

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