For the first time in 34 years, the U.S. and Philippines will not hold the annual amphibious joint exercise PHIBLEX in 2017, the latest sign of strain in the two countries' relationship since Philippine President Rodrigo Duterte was elected in May.

More than 1,400 Okinawa-based Marines and sailors from the 3rd Marine Expeditionary Brigade, and 500 Philippine troops participated in the 33rd annual PHIBLEX this October. The annual exercise involved live-fire events, as well as training for amphibious landings.

But in 2017, the two countries will hold a different training exercise, one that is more limited in scope and focused on amphibious operations in response to natural and man-made disasters, officials said.

"PHIBLEX included a wider range of capabilities, ranging from command and control, mobility, maneuver, logistics, and territorial defense to humanitarian assistance and disaster relief missions," said Chuck Little, a spokesman for Marine Corps Forces, Pacific.

The exercises slated for 2017 will include training for cybersecurity, maritime security and counter terrorism, said Capt. Rachel Nolan, a liaison officer for the U.S. in Manila. 

"We reached a mutually agreed upon plan for 2017, which ensures that U.S.-Philippine military training activities and engagement remain robust and substantial," Nolan said.

Relations between the U.S. and the Philippines have been strained since Duterte was elected in May. He has ordered a crackdown on alleged drug users and dealers that has resulted in thousands of deaths. President Obama canceled a meeting with Duterte after the Philippine president vowed to swear at Obama if he expressed concerns about those killed.

Duterte initially vowed to end all military training exercises with the U.S., but the two countries so far have agreed to cancel only a small number of them — including PHIBLEX and CARAT, a Navy exercise. The shift is driven by the Filipino president's desire not to appear confrontational toward China, said Carl Baker a defense analyst with the Center for Strategic and International Studies.

"They've said: 'We don't want to do patrols in the South China Sea and we don't want to do maritime-based exercises that focus on assault and amphibious landings," said Baker, director of programs at Pacific Forum CSIS in Honolulu.

But, Baker added, ""The fact is there is still a deep engagement with the Philippines."

The U.S. military relationship with the Philippines is shifting back to its original focus on being prepared for humanitarian assistance and disaster relief missions, Baker said.

"That's what we always used to do, and that's what we do with Balikatan, and that's why they didn't cancel Balikatan," he said, referring to another joint military exercise between the two countries.

In September, Defense Secretary Ash Carter called the relationship between the U.S. and the Philippines ""ironclad;" however, Philippine Defense Minister Delfin Lorenzana told reporters on Dec. 8 that his country would likely not allow U.S. ships and planes to use his country for patrols in the South China Sea.

The rough patch between the U.S. and the Philippines may turn out to be short-lived. Duterte seems to enjoy a much warmer relationship with President-Elect Donald Trump, who has reportedly invited Duterte to the White House.

It is important to weigh what Duterte says in public with what he actually orders his military to do, said retired Army Special Forces Col. David Maxwell, associate director at the Center for Security Studies at Georgetown University.

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"If he is allowing exercises to continue, albeit with a new name and a new concept, I think it indicates he wants to sustain the military alliance," Maxwell said.

The U.S. military alliance with the Philippines expanded significantly under Duterte's predecessor. In March, the two countries announced plans for a permanent American military presence and five military bases that will support rotational deployments of U.S. forces near the contested South China Sea.

Military leaders view the Philippines as a key ally for containing China and its territorial ambitions in the South China Sea.