Donald Trump had wanted to have Syrian President Bashar al-Assad killed in 2017, while he had previously denied it.
The US president told Fox News on Tuesday that he was ready, but that then-defence Secretary Jim Mattis did not want to do it.
Trump says he does not regret that he did not persevere. In the interview, he lashed out again at Mattis, calling him “very overrated, a bad person, a terrible general and a bad leader”.
Mattis resigned in December 2018 out of dissatisfaction with Trump’s decision to withdraw US troops from Syria.
In a 2018 book, journalist Bob Woodward wrote that Trump had urged Mattis to plan to liquidate Assad after chemical attacks on civilians by the Syrian military, but Mattis held back.
The US eventually fired cruise missiles at Syria. Trump said in September 2018 that the killing of Assad had not even been considered. He called the book “fiction”.