Sean Penn thinks Donald Trump wants to "destroy the world".

The 'Milk' actor - who has been an outspoken critic of the president - has given a warning about the "worst case scenarios" that could happen under the former 'Apprentice' star's current second term as US leader as he discussed Trump's plans to deport American citizens to El Salvador's notorious CECOT prison.

Speaking to Jim Acosta on the journalist's self-titled podcast, he said: "Before [Salvadoran President Nayib Bukele] gets to that point where he's dealing with another leader, we should consider worst-case scenarios.

"I do think it's a reasonable theory that Donald Trump is not unlike the spouse of someone who leaves him, perhaps for another, who then murders their former partner, because if they can't have her, nobody can.

"I think Donald Trump, in his solipsism, may have that relationship with the world, and that this destruction is in part a power play, and also a literal intention of his final out."

Trump has previously hinted at attempting to defy the constitution and run for a third term as president, and the 67-year-old actor doesn't think the 78-year-old commander-in-chief's plans will have positive consequences.

Asked about the possibility of a third term, he said: "I think he might try to destroy the world before he ages out of life."

Sean appeared on the podcast to promote 'Words of War', a biographical drama he has executive produced which stars Jason Isaacs and Maxine Peake, and tells the story of late Russian journalist and human rights activist Anna Politkovskaya, who defied intimidated to fight to expose corruption in her home country but was assassinated outside the elevator of her Moscow apartment in 2005.

And the Oscar-winning star urged people who think such shocking events wouldn't happen on US soil to think again.

He warned: "Those who think it can't happen here either have not studied the certain indications that it will, unless people are involved and they're educated.

"We are tasting in our country what the Russians have gone through."