The Philippines and the United States began annual joint military exercises Tuesday in what could be the last time the once close allies hold war games amid increasingly tense relations between Manila and Washington. 

President Rodrigo Duterte said last week the Philippines would no longer hold military exercises with the U.S. after Washington criticized his bloody war on drugs. Since taking office for a six-year term in June, more than 3,000 people have been killed in violent drug busts. Duterte went further Tuesday, telling President Barack Obama to "go to hell" and saying he would rather the Philippines pursue an alliance with China and Russia. 

"I have lost my respect for America," Duterte said. "Eventually I might in my term, break up with America. I would rather go to Russia or to China. Even if we do not agree with their ideology, they have respect for the people. Respect is important."

For Washington, the Philippines has long represented a strategic alliance in Asia, and that continues to hold true, with China increasingly demanding sovereignty over disputed territory in the South China Sea, one of the world's most important shipping routes, and with North Korea holding more frequent nuclear tests. Benigno Aquino, Duterte's predecessor, filed a case with the United Nations this summer contesting China's claims over the entire South China Sea.

Under a mutual defense treaty dating back to 1951, the Philippines and United States meet every two years for military exercises. During the event this week, the Philippines military and U.S. Marines are slated to spend time together in the northern island of Luzon through Oct. 12, Reuters reported. Roughly 1,100 American and 400 Filipino troops were invited. The Philippines is the third-largest Asian recipient of U.S. military aid after Afghanistan and Pakistan.

"We share a unique and enduring bond in this region, and each year we are offered an invitation to strengthen our relationship during (these exercises)," U.S. Marine Brigadier General John Jansen said in a speech.

A U.S. embassy official said Tuesday both nations would continue to work together. "We're continuing to work with our partners on our bilateral relationship as we know it to be and as it has existed for decades," embassy official Emma Nagy said.

But Duterte has frequently complained in recent weeks about the U.S., a former colonial ruler of the Philippines, at one point even calling Obama a "son of a bitch."

"The Americans, I don't like them... they are reprimanding me in public. So I say: 'Screw you, f--- you'," he said Sunday.