The Islamic Republic of Iran’s efforts to assassinate President Donald Trump were far more widespread than initially reported, as was the president’s concern over the possibility of another attempt on his life.

In his upcoming book, Revenge: The Inside Story of Trump’s Return to Power, Politico reporter Alex Isenstadt reveals that he had “extensive access” to Trump’s inner circle during his campaign.

“Law enforcement officials warned Trump last year that Tehran had placed operatives in the U.S. with access to surface-to-air missiles,” he wrote in a report published at Axios. “Trump’s team worried that the Iranians could try to down his easily recognizable personal jet — better known as ‘Trump Force One’ — as it was taking off or landing.”

Their concern that Iran might try to shoot down his airplane grew stronger after he survived a foiled assassination attempt at his golf course in Palm Beach, Florida.

The threat was deemed so serious that, on at least one occasion, the Secret Service arranged for Trump to fly on a different plane instead of his own.

Trump’s plane was used as a decoy, carrying several of his aides on board, the report said, quoting the book.

In another previously undisclosed incident, the Secret Service shot down a drone that had been following Trump’s motorcade, using an electromagnetic weapon to disable it.

These threats from Iran come amid Trump’s warning last week that he would unleash “all hell” on the country if they attempted to assassinate any current or former U.S. officials.

Trump stated last week that he has provided instructions for the U.S. military outlining their actions if he is assassinated by Iran.

“And that would be a terrible thing for them to do,” he said. “Not because of me, because if they did that, they would be obliterated. That would be the end. I’ve left instructions — if they do it, they get obliterated. There won’t be anything left.”