The leaked transcript from the Philippines' foreign affairs department shows during an April 29 phone call between the two leaders, Trump congratulated Duterte for his "great" and "unbelievable" job in the campaign against drugs, USA Today reported.
"I just wanted to congratulate you because I am hearing of the unbelievable job on the drug problem," Trump says, according to the transcript. "Many countries have the problem, we have a problem, but what a great job you are doing and I just wanted to call and tell you that."
Less than a year after Duterte assumed office, more than 7,000 suspected drug dealers and users had died, rights groups have said.
Trump had called Duterte after the conclusion of the summit of the Association of Southeast Asian Nations, Philippine news service ABS-CBN News reported.
"He is not stable, Mr. President, as he keeps on smiling when he explodes a rocket. He even has gone against China which is the last country he should rebuke," Duterte said in response to Trump's question.
Trump then told Duterte U.S. military might is on standby in case of war, but also expressed reservations about deploying them in a conflict.
"We have a lot of firepower over there. We have two submarines – the best in the world – we have two nuclear submarines – not that we want to use them all. I've never seen anything like they are but we don't have to use this but he could be crazy so we will see what happens," Trump said.
Duterte said, "every generation has a mad man," then described Kim as a "very delicate problem."
Duterte fell under strong U.S. criticism before Trump assumed office, and former President Obama refused to meet with Duterte because of what three U.S. senators described in a letter to the U.S. State Department as a "campaign of mass atrocities thinly disguised as a response to a public health emergency," according to The New York Times.