MANILA - It was, in the end, another joke meant to take journalists for a ride.

After claiming that he promised God on a plane from Tokyo that he would stop swearing, and then breaking that vow after just one long weekend, President Rodrigo Duterte said on Friday (Nov 4) "only fools" would believe he actually talked to God.

In a speech before lawyers, he said it was a "joke", one of the those preposterous statements he likes to make and then retract later.

"Those fools, they believed me," he said. "I'm no Bar top-notcher, but I'm not an idiot," he said, referring to the exams administered to aspiring lawyers.

He said it was just one of those "pranks" he used to play on the media when he was a city mayor.

In a news conference on October 27, shortly after visiting Japan, Mr Duterte said he heard a voice he believed was God's telling him the plane he was on would crash unless he stopped cursing.

So, he agreed to watch his tongue. "A promise to God is a promise to the Filipino people," he said.

For a few days, Mr Duterte appeared to honour that pledge, holding himself back when he was on the verge of mouthing an expletive.

But on Monday (Oct 31), he cursed at some police officers. "Never enter into illegal drugs," he told them. "Son of a whore, I will kill you, I'm telling you."

By Wednesday (Nov 2), he was back in prime cursing form after receiving reports that US Senator Ben Cardin was blocking the sale of some 26,000 assault rifles to the Philippine police.

For good measure, he also called those behind the move "fools" and "monkeys".