Fidel Ramos — a former president of the Philippines who was tapped by incumbent Rodrigo Duterte to serve as a special envoy to China — resigned this week after penning a scathing opinion piece referring to Duterte as “full of S…. T!!!” regarding his foreign policy.

Ramos, who the outlet Quartz notes played a pivotal role in convincing Duterte to run for president of the Philippines when he was still serving as mayor of southern Davao City, has also referred to Duterte as a “huge disappointment.” Ramos has pilloried Duterte’s foreign policy following multiple profane tirades in which Duterte has vowed to cut ties with the United States and become “best friends” with the leaders of China and Russia.

Duterte made his first trip abroad as president last month to China, where he promised to set aside a bilateral dispute over the Philippine territory of the South China Sea, which China claims as its own. The Permanent Court of Arbitration at the Hague found earlier this year that China’s claims in the region were invalid, and China’s presence in disputed waters was illegal.

“In his consistently frequent insulting diatribes against the US, EU, and the UN… he is unwittingly shooting himself in the mouth, and also all of us, 101.5 million Filipinos,” Ramos wrote in a column published in late October, according to Singapore’s Straits Times. The Manila Bulletin carried the full article, in which Ramos protests Duterte’s reluctance to adhere to international climate change agreement standards in particular. He calls Duterte “obviously wrong, and full of S…. T !!!” for not pushing to ratify the Paris agreement.

In separate comments, Ramos referred to Duterte’s approach to the head of state job as a “huge disappointment and let-down.” In particular, Ramos challenged Duterte’s belligerence towards the United States: “Are we throwing away decades of military partnership, tactical proficiency, compatible weaponry, predictable logistics and soldier-to-soldier camaraderie just like that?”

Ramos also protested against Duterte’s harsh words towards UN Secretary General Ban Ki-Moon. Duterte has said he does not “give a shit” about the UN questioning the human rights violations occurring as part of his war on drugs.

“When he cussed Secretary-General Ban Ki-moon of South Korea, many of us who are Korean veterans of the Korean War of 1950-53 felt hurt,” Ramos said of his comments. Ramos also praised President Barack Obama for being “the first black American to make it all the way to the top. It’s like a Mindanaoan making it all the way to the top to Malacañang.”

Duterte is the nation’s first president from the southern island of Mindanao. He has repeatedly referred to President Obama as a “son of a whore.”

In late October, upon his return from a diplomatic trip to Japan, Duterte said that he heard God command him to stop using profanity in public and that he would no longer be so loose with his language.

“I know he is pro-Western. He is a military man who studied there (in the US). You must remember Ramos finished his (studies) in West Point. He really does not want to fight (with the US),” Duterte said of Ramos, lamenting his departure this week.