Levinson disappeared in Iran under mysterious circumstances more than a decade ago, and though U.S. diplomats and investigators have long said they thought he was taken by Iranian government agents, Monday’s announcement in the final weeks of the Trump administration was the most definitive assignment of blame to date.

Besides blaming two high-ranking intelligence officers by name, U.S. officials also said the Iranian regime sanctioned the plot that led to Levinson’s abduction and lied for years about its involvement in his disappearance through disinformation campaigns aimed at deflecting responsibility and covering up the government’s role.

“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 in a statement. “The United States will always prioritize the safety and security of the American people and will continue to aggressively pursue those who played a role in Mr. Levinson’s detention and probable death.”

The two Iranian intelligence officers, identified as Mohammad Baseri and Ahmad Khazai, are both allege to have been involved in his abduction. Under sanctions announced Monday, any property or assets that they hold in the United States would be blocked. Though it’s unlikely that they have bank accounts in the U.S., the sanctions could also limit their movements or financial dealing outside of Iran. The men have met with intelligence officials from other countries and also led delegations, U.S. officials say.

There was no immediate reaction in Iranian state media Monday night to the announcement.

In a statement, the Levinson family thanked Trump administration officials and vowed to hold accountable anyone responsible for his death.

“Robert Levinson will never come home to his family alive because of the cruel, cynical and inhumane actions of the Iranian authorities,” the family 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.”

Monday’s announcement is just the latest in a series of increasingly aggressive Trump administration actions against Iran since the president withdrew from the landmark 2015 Iran nuclear deal two years ago.

Since President Donald Trump pulled out of the deal — a signature foreign policy achievement of predecessor Barack Obama — in 2018, his administration has steadily ramped up pressure on Iran, re-imposing a wide swath of sanctions and taking other actions, including killing the head of the Islamic Revolutionary Guards Corps in a drone strike at the airport in Baghdad this year.

That move, coupled with retaliatory attacks against Iranian-backed militias in Iraq, stepped up sanctions against Iranian proxies in Lebanon and Yemen and the recent killing of an Iranian nuclear scientist outside of Tehran that has been attributed to Israel, have left the impression that Trump is seeking to box in President-elect Joe Biden when he takes office in January.

Biden has said he wants to reenter the 2015 nuclear deal but also improve and expand on it. Those prospects may prove difficult to realize if the situation escalates in the next five weeks.

Officials said they were acting now, one month before Trump leaves office, not for any political reasons but simply because they had finally accumulated enough information to formally hold Iran accountable. They also said that no agreement with Iran should be reached in the next administration without a deal to free the remaining handful of U.S. citizens imprisoned there.

The announcement comes nine months after U.S. officials revealed that they had concluded that Levinson “may have passed some time ago” though they did not disclose at the time the information that led them to that assessment.

Officials on Monday would not describe any additional information that led them to believe Levinson had died in captivity, except to say that all evidence they had pointed in that direction, or how they came to identify the role of the two individual intelligence officers.

Levinson vanished on March 9, 2007, when he was scheduled to meet a source on the Iranian island of Kish. For years, U.S. officials would say only that Levinson was working independently on a private investigation. But a 2013 Associated Press investigation revealed that Levinson had been sent on a mission by CIA analysts who had no authority to run such an operation.

The family received a video in late 2010 as well as proof-of-life photographs in 2011 in which he appeared disheveled with a long beard and wearing an orange prison jumpsuit like those given to detainees at the Guantanamo Bay prison. Even then, his whereabouts and fate were not known, and the Iran government has persistently denied having any information about Levinson.

Earlier this year, a federal judge in Washington held Iran liable for his disappearance, saying the country was “in no uncertain terms” responsible for Levinson’s “hostage taking and torture.”

In November 2019, the Iranian government unexpectedly responded to a United Nations query by saying that Levinson was the subject of an “open case” in Iranian Revolutionary Court. Although the development gave the family a burst of hope, Iran clarified that the “open case” was simply an investigation into his disappearance.