“I am a president of a sovereign state and we have long ceased to be a colony. I do not have any master except the Filipino people, nobody but nobody,” Duterte told reporters.

“You must be respectful. Do not just throw questions. Putang ina, I will swear at you in that forum.”

“Putang ina” is the Tagalog phrase for son of a bitch.

Rodrigo Duterte is well known for having a “bad mouth”. The Philippine president will not hesitate to swear at anyone even in public – no matter the status – if you dare provoke him.

The least public show Obama would want the world to see at the G20 summit, is a face-off with either Russia’s Putin or Philippine’s Duterte. So it’s more likely that Mr. President has decided to tarry for a while and see if the waters will calm down.

Earlier in May, Duterte boldly called the pope a “son of a whore”. In June, he verbally attacked United Nations and its Secretary General Ban Ki-moon for their criticisms against Philippine’s government.

Duterte said UN is “a stupid organization“, threatening that his government will withdraw from the union “if you are that disrespectful, son of a bitch”.

The tension has continued to build up this week after Duterte warned that President Barack Obama should dare not ask him about his government’s recent extrajudicial killings in its war against drug dealers and drug users.

The Philippine’s president said: “Son of a bitch, I will swear at you,” if you dare.

President Barack Obama eventually called off a planned meeting with Duterte on Tuesday, hoping to carefully avoid any unnecessary confrontation with the U.S. ally as world leaders take part in a diplomatic tour of Laos.

Duterte’s remarks were made just before he was scheduled to fly to Laos for the Association of Southeast Asian Nations summit.

It’s unusual for one president to tell another what to say or not say, and much rarer to call the other a “son of a bitch.” Duterte managed to do both just before flying to Laos for a regional summit, warning Obama not to challenge him over extrajudicial killings in the Philippines, The Atlantic wrote.

“I have seen some of those colorful statements in the past, and so, clearly, he’s a colorful guy,” Obama said. “What I’ve instructed my team to do is talk to their Philippine counterparts to find out is this in fact a time where we can have some constructive, productive conversations.”

Early Tuesday, National Security Council spokesman Ned Price said the meeting with Duterte has been canceled till further notice.

The U.S. president spoke during a news conference in Hangzhou, China, after the Group of 20 Summit there, calling the Philippines an ally.

Obama also admitted his relationship with the Philippine people has been “extraordinarily warm and productive.”

Obama said Monday that he would “undoubtedly” bring up Duterte’s war on drugs, human rights, and concerns for due process, should the two leaders eventually meet.

“We recognize the significant burden that the drug trade plays just not just in the Philippines, but around the world.

“We will always assert the need to have due process and to engage in that fight against drugs in a way that’s consistent with basic international norms. And so, undoubtedly, if and when we have a meeting, that this is something that’s going to be brought up, and my expectation, my hope is, is that it could be dealt with constructively.”

The Associated Press added that managing Duterte has become a worsening headache for Obama since the Filipino took office on June 30, pledging his foreign policy wouldn’t be constricted by reliance on the U.S.

Washington has tried largely to look the other way as Duterte has pursued closer relations with China, a marked shift for the Philippines considering recent tensions over Beijing’s aspirations in the South China Sea.

Nevertheless, Duterte personally disclosed that he suffers from Buerger’s disease, an inflammation of blood vessels mostly in the limbs that has been traced to previous habitual smoking, contrary to earlier rumors of throat cancer.