Metro Manila (CNN Philippines, December 3) — President Rodrigo Duterte said he uses marijuana to keep up with the grueling schedules in meetings with other heads of states.

"It's a killing activity. And I think … my age, ako, hindi masiyado, kasi nagma-marijuana ako eh para magising [me, not much because I use marijuana to keep awake]," Duterte said Monday during the conferment of awards on the Association of Southeast Asian Nations (ASEAN) National Organizing Council officials and personnel.

Duterte later clarified in a chance interview with reporters that he was only joking about using marijuana.

"Of course it was a joke. Pero nobody can stop me from just doing my style. Minsan sabi ninyo mysoginist ako, magbiro ako ng ganun (like that). That's my style. It's too late to change. If I want to joke, I will joke," he said. "Ngayon, kung maniwala kayo, eh g*** kayo. (If you believe it, then you're dumb.)"

Senator Koko Pimentel also said in a text message that Duterte told him during the conferment of the Quezon Service Cross for the late Senator Miriam Defensor-Santiago that "he has never touched marijuana his entire life."

In his speech, Duterte was complaining of the tight schedules in previous meetings, such as in his visits to Thailand, India and Papua New Guinea, saying in Tagalog he "could not handle this."

"Hindi talaga kaya, nung ako dito. I just never, I remember I just came in from nowhere, then kinabukasan umpisa na. I think I was in India. Susmaryosep, walang tulog. And the more the crescendo becomes faster, mas lalong hindi ka nakakatulog kasi nga hinahabaol ka ng babasahin," Duterte said.

[Translation: I couldn't take it when I was there. I just never, I remember I just came in from nowhere, then the next day it started. I think I was in India. Oh my God, I had no sleep. And the more the crescendo becomes faster, the more that you wouldn't be able to sleep because you are catching up on readings.]

Duterte suggested that only the "important, the most urgent, the most immediate" should be tackled in summits, while other matters should be left to a technical working group or the "lower echelons."

The President is known for his tough stance on drugs and has waged a bloody war against it, drawing criticisms from human rights groups. According to government data, close to 5,000 drug suspects have been killed in legitimate police operations.

Duterte is against the recreational marijuana, but is open to legalizing medical marijuana.

The possession and use of marijuana is illegal in the Philippines and can be punished by up to life imprisonment and a ₱10 million fine.

CNN Philippines' Ina Andolong, Joyce Ilas and Xave Gregorio contributed to this story.