The U.S. State Department announced a $20 million reward on Thursday for information leading to the arrest of the alleged Iranian mastermind behind a plot to assassinate former White House official John Bolton.

U.S. officials said in August 2022 that they had uncovered a plot by Shahram Poursafi, a member of Iran's Islamic Revolutionary Guard Corps (IRGC), to kill Bolton, who served as national security adviser to former President Donald Trump.

The State Department's Rewards for Justice program "is offering a reward of up to $20 million for information leading to the arrest or conviction" of Poursafi, a notice said Thursday.

The move came as Trump, 78, who is running for a new White House term, claimed there were "big threats" on his life by Iran.

Bolton, considered a foreign policy hawk, is a fierce critic of Iran and advocated that Trump unilaterally withdraw from the Iran nuclear deal in 2018.

Poursafi allegedly offered an unidentified person inside the United States $300,000 to kill Bolton in the capital area.

The plan was likely set in motion after the U.S. killing of top IRGC commander Qassem Soleimani in Iraq in January 2020, the Justice Department said at the time.

But it never made headway because the ostensible assassin became an informant of the Federal Bureau of Investigation.

Iranian authorities have dismissed the allegations as "fiction."

The United States designated the entire IRGC a "foreign terrorist organization" in 2019, after previously designating its external operation, the Quds Force.