Dan Levinson, of Coral Springs, Fla., is the eldest son of Robert Levinson. His family runs the website helpboblevinson.com.

The United Nations Working Group on Arbitrary Detention, which investigates cases of arrest that may be in violation of international human rights law, did something in January that the previous two U.S. presidents failed to do: It announced a finding that my father, retired FBI agent Robert Levinson, was arrested by Iranian authorities without any legal grounds in March 2007 on Kish Island, and it called on the Iranian government to release him immediately.

In finding that Iran has violated international law — and fundamental human decency — by detaining a U.S. citizen and providing him no rights whatsoever, the U.N. working group is being far more aggressive than our own U.S. government has been in 10 years. This is shameful.

We desperately need President Trump to succeed now where his two predecessors failed. Last March, then-candidate Trump stated Iran “absolutely” knows where my father is. He also spoke of how he believed my dad might be released before he even took office. While that unfortunately did not happen, this is still one of Trump’s first foreign policy opportunities to demonstrate American strength.

The U.N. working group, in issuing its opinion, confirmed what we already knew. Since their prisoner deal in January 2016, U.S. and Iranian officials held just one meeting focused on my dad, despite the two countries pledging to cooperate on his case. Following that single meeting last April, our family was informed by U.S. officials involved in the talks that the Iranians told our government that there was no reason to meet again and essentially that they would let our government know if they hear anything new. What was just as concerning was how the administration let them off the hook and didn’t force the Iranians back to the table until just before President Barack Obama was leaving office.

In January, my family was told that negotiations were taking place to secure my dad’s release, and once again we held our breath. However, it was too little, too late: The Iranians walked away, apparently believing that they could make a better deal with our new president. Obama had eight years to get my father out, and it is now obvious that he was never a true priority. Most damning of all, neither Obama nor then-Secretary of State John Kerry ever said publicly that they believed Iran arrested my dad, even though it is what officials have told our family from the beginning. We must demand much, much more from the Iranian government.

For those who wonder how, or whether, my father has survived during this time, I would make three points: First, it is unlikely that the Iranians have allowed any harm to come to him in prison, because he is deal material. If they let him die in captivity, the international outcry would be too immense once the media inevitably found out. Second, those doubting my father’s ability to survive had the same questions just a few years ago — and suddenly photographs and a video showed him to have survived years of captivity. He has a wife of 42 years, seven children and a growing number of grandchildren he desperately wants to come home to. And last but most important, FBI officials tasked with the day-to-day investigation, who have seen the evidence for nearly 10 years, have told our family they believe he is alive, in Iran, and — ironically — that his earlier health concerns of hypertension and diabetes likely have been resolved due to his “limited” diet in captivity.

As a dealmaker, Trump has the skill and experience to negotiate the agreement Obama couldn’t — to secure my dad’s release in his first 100 days. If Iran continues to deny holding him and fails to act, Trump can pressure it with tools such as sanctions — which he demonstrated his willingness to use already – or labeling Iran’s Islamic Revolutionary Guard Corps, which was very likely involved in my father’s detention, a terrorist organization. Trump can put my father at the center of every single discussion he has with or about Iran and finally make him a top priority — not just in words like the previous administration, but in action.

It is virtually impossible for someone, especially a 6-foot-4, blue-eyed foreigner with a U.S. passport, to simply vanish on a tiny Iranian island with heavy security, but the Iranians continue to claim this is what happened. There are people in the Iranian government who were directly involved in his arrest, just as there are people there now who can easily order his return home to us.

My father is an American patriot who sacrificed so much for his country in more than three decades of service. The Iranian government took him hostage and has been getting away with it without repercussions for a decade. Every American should be outraged at this atrocity. Every American should know the name Robert Levinson and mandate our government’s action. And yet, he has been left behind by the U.S. government over and over and over.

Our family knows we can’t bring him home by ourselves. The U.N. working group’s opinion was a much-needed, important step, but now the United States must greatly ramp up the pressure. After 10 years, we must stand up to Iran and put Robert Levinson first. We must end my father’s suffering by demanding that he finally be brought home.