The Trump administration imposed sanctions Monday on two Iranian intelligence officials it holds responsible for the abduction, detention and probable death of Robert Levinson, a former FBI agent who disappeared in Iran almost 14 years ago.

Senior U.S. officials provided no evidence for their claims, so as not to compromise intelligence sources. The two officials designated are high-ranking officers in the Ministry of Intelligence and Security, the Iranian equivalent of the CIA.

The U.S. officials said the decision to publicly assign blame in Levinson’s disappearance now, in the final weeks of President Trump’s time in office, was related to new information and the lengthy process of getting government lawyers to approve the decision.

But the timing also appears to be an attempt to narrow the parameters of any potential negotiations if President-elect Joe Biden seeks to rejoin the nuclear agreement with Iran that Trump abandoned in 2018. At least three Americans are currently detained in Iran.

“There should be no agreement negotiated with Iran ever again that doesn’t free Americans who are unjustly detained in that country,” said one of the senior U.S. officials, speaking on the condition of anonymity under rules imposed by the White House. “We all expect negotiations next year. That negotiation must include the return home of all the Americans unjustly detained in that country.”

Levinson, who would be 72 if he is alive, disappeared under murky circumstances in March 2007 while on Kish Island, a tourist spot off the coast of Iran. He was there on an unauthorized trip for the CIA to gather intelligence on Iran’s nuclear program.

Levinson, who had spent 28 years working for the FBI and the Drug Enforcement Administration, was last seen alive nearly a decade ago when he appeared in a hostage video dressed in an orange prison suit. The Iranian government has repeatedly denied any involvement in his abduction and detention.

But both the Levinson family and U.S. officials who work on hostage matters have for some time concluded that he died in captivity. The State and Justice departments have jointly offered $25 million for information leading to his discovery and return. U.S. officials told reporters they hoped naming the Iranian intelligence officers, Mohammad Baseri and Ahmad Khazai, would encourage more people to come forward with tips leading to his location.

“The truth is that Iranian intelligence officers — with the approval of senior Iranian officials — were involved in Bob’s abduction and detention,” FBI Director Christopher A. Wray said in a statement released by the Treasury Department. “While no one should be as cruelly treated as Bob was, this situation is personal because Bob served as a special agent for 22 years and will always be a part of the FBI family. We will never waver from our commitment to find out more about Bob’s long captivity, to give the Levinson family the answers they deserve, and to finally bring Bob home.”

The Treasury Department said Baseri and Khazai were involved in Levinson’s abduction, which it said was authorized by senior Iranian officials.

“The abduction of Mr. Levinson in Iran is an outrageous example of the Iranian regime’s willingness to commit unjust acts,” Treasury Secretary Steven Mnuchin said.

The Levinson family issued a poignant statement thanking the Trump administration — particularly the men and women of the FBI who have worked on his case — and made clear that they, too, believe he has died.

“Robert Levinson will never come home to his family alive because of the cruel, cynical and inhumane actions of the Iranian authorities,” the statement said. “Because of these men and others like them, our wonderful husband, father and grandfather died alone, thousands of miles from everyone he loved. This is just one step in a long road toward achieving justice for him, but it is an important one.”

“No matter how long it takes,” they added, “we will find the individuals who are responsible for what happened to Bob Levinson, and we will hold them accountable.”

Trump and Secretary of State Mike Pompeo have been harshly critical of the Obama administration for finalizing the 2015 nuclear agreement with Iran without demanding information on Levinson and the release of Baquer Namazi, 84, and his son Siamak. The Namazis, who hold dual citizenship, have languished in an Iranian prison for more than five years after being convicted of ­espionage-related charges. Morad Tahbaz, an Iranian American conservationist, was seized in 2018 and convicted the following year for “contacts with the U.S. enemy government.”

“The Iranian regime has a 41-year history of abducting and detaining foreigners and dual-nationals as political leverage,” Pompeo said in a separate statement. “We reiterate our strong warning to U.S. citizens and dual-nationals that traveling to Iran may jeopardize their personal safety. The abduction, detention, and probable death of Mr. Levinson is another egregious example of the regime’s callous disregard toward human life.”

Relations between Washington and Tehran have been on a downward spiral since Trump withdrew from the nuclear accord and began imposing a long string of sanctions aimed at getting Iran to renegotiate the nuclear deal, stop arming militants in the region and rein in its ballistic missile testing. Even as Iran’s economy has crumbled, the government has stepped up its nuclear program beyond the limits it agreed to in the nuclear deal.

As the Trump administration’s days dwindle, the United States has accelerated its “maximum pressure” campaign of economic sanctions on Iran, so far to no avail.