His revolutionary fervor diminished by the years that have also turned his dark brown hair white, one of the Iranian student leaders of the 1979 U.S. Embassy takeover says he now regrets the seizure of the diplomatic compound and the 444-day hostage crisis that followed.

Speaking to The Associated Press ahead of Monday's 40th anniversary of the attack, Ebrahim Asgharzadeh acknowledged that the repercussions of the crisis still reverberate as tensions remain high between the U.S. and Iran over Tehran's collapsing nuclear deal with world powers.

Asgharzadeh cautioned others against following in his footsteps, despite the takeover becoming enshrined in hard-line mythology. He also disputed a revisionist history now being offered by supporters of Iran's Revolutionary Guard that they directed the attack, insisting all the blame rested with the Islamist students who let the crisis spin out of control.

"Like Jesus Christ, I bear all the sins on my shoulders," Asgharzadeh said.

At the time, what led to the 1979 takeover remained obscure to Americans who for months could only watch in horror as TV newscasts showed Iranian protests at the embassy. Popular anger against the U.S. was rooted in the 1953 CIA-engineered coup that toppled Iran's elected prime minister and cemented the power of Shah Mohammad Reza Pahlavi.

The shah, dying from cancer, fled Iran in February 1979, paving the way for its Islamic Revolution. But for months, Iran faced widespread unrest ranging from separatist attacks, worker revolts and internal power struggles. Police reported for work but not for duty, allowing chaos like Marxist students briefly seizing the U.S. Embassy.

In this power vacuum, then-President Jimmy Carter allowed the shah to seek medical treatment in New York. That lit the fuse for the Nov. 4, 1979, takeover, though at first the Islamist students argued over which embassy to seize. A student leader named Mahmoud Ahmadinejad, who later became president in 2005, argued they should seize the Soviet Embassy compound in Tehran as leftists had caused political chaos.

But the students settled on the U.S. Embassy, hoping to pressure Carter to send the shah back to Iran to stand trial on corruption charges. Asgharzadeh, then a 23-year-old engineering student, remembers friends going to Tehran's Grand Bazaar to buy a bolt cutter, a popular tool used by criminals, and the salesman saying: "You do not look like thieves! You certainly want to open up the U.S. Embassy door with it!"

"The society was ready for it to happen. Everything happened so fast," Asgharzadeh said. "We cut off the chains on the embassy's gate. Some of us climbed up the walls and we occupied the embassy compound very fast."

Like other former students, Asgharzadeh said the plan had been simply to stage a sit-in. But the situation soon spun out of their control.