DUBAI, United Arab Emirates — An Iranian-American journalist who once worked for a U.S. government-funded broadcaster is believed to have been detained by Iran for months now, authorities said Sunday, further raising the stakes as Tehran threatens to retaliate over an Israeli attack on the country.

The imprisonment of Reza Valizadeh was confirmed to The Associated Press by the U.S. State Department as Iran marked the 45th anniversary of the takeover of the American Embassy and hostage crisis on Sunday.

It also followed a threat by Iranian Supreme Leader Ayatollah Ali Khamenei a day earlier to provide “a crushing response” to Israel and the U.S. as long-range B-52 bombers reached the Middle East in an attempt to deter Tehran.

Valizadeh had worked for Radio Farda, an outlet under Radio Free Europe/Radio Liberty that’s overseen by the U.S. Agency for Global Media.

In February, he wrote on the social platform X that his family members had been detained in an effort to make him return to Iran. In August, Valizadeh apparently posted two messages suggesting he had returned to Iran despite Radio Farda being viewed by Iran’s theocracy as a hostile outlet. “I arrived in Tehran on March 6, 2024.

Before that, I had unfinished negotiations with the (Revolutionary Guard’s) intelligence department,” the message read in part. “Eventually I came back to my country after 13 years without any security guarantee, even a verbal one.” Valizadeh added the name of a man who he cl.