"I'd be happy to slaughter them. At least if Germany had Hitler, the Philippines would have (me)," Duterte said Friday while speaking in his hometown of Davao City. "You know my victims, I would like (them) to be all criminals, to finish the problem of my country and save the next generation from perdition."
Asked about Duterte's comments Friday, Secretary of Defense Ash Carter called them "deeply troubling."
Speaking to reporters after attending a meeting of defense ministers from the Association of Southeast Asian Nations, in Oahu, Hawaii, Carter said Duterte's remarks were not discussed in the meeting. He stressed that US-Philippines cooperation would continue, saying, "It has served the interests of our nations for many years now" and adding that he had good discussions about "ongoing alliance operations" with his counterpart from the Philippines.
Carter's description of Duterte's remarks were echoed earlier Friday by State Department spokesman Mark Toner.
"We find them troubling," Toner told reporters in Washington.
Toner went on to say that the US-Philippines relationship was based on "our shared belief in human rights and human dignity, and within that context, President Duterte's comments are a significant departure from that tradition."
He added, "Words matter, especially when they're from leaders of sovereign nations."
But when asked if the latest Filipino leader's outburst would negatively affect the US-Philippines relationship, Toner said the US government continues to "productively, constructively and closely cooperate with the Philippines on a number of issues."
He continued, "While there (are) these remarks occasionally being made, at the working level our relationship remains very strong and very vital."
Toner highlighted security cooperation as one such area that remained strong, comments that followed remarks Thursday by Secretary of Defense Ash Carter describing the two countries' military relationship as "ironclad."
Still, Duterte himself has cast doubt on the future of that collaboration, and his incendiary comments and aggressive style of rule could complicate the relationship with the US.
Duterte, speaking in Hanoi, Vietnam, earlier this week, said joint US-Philippine navy drills scheduled for next month will the last of its kind between the two countries.
"I would serve notice to you now that this will be the last military exercise. Jointly, Philippines, US, last one," he said, while noting that such exercises are not wanted by China.
While defense officials from both the Philippines and the US downplayed the immediate impact of the President's statements, his comments are bound to complicate a relationship that the US has long seen as one of its most stable in Southeast Asia.
The US and the Philippines are co-signatories of a mutual defense pact, signed in 1951. Duterte signaled that he would continue to honor the pact while speaking in Vietnam, noting it dates back to the 1950s, even as he said he would "establish new alliances for trade and commerce."
But as the US seeks allies amid China's increasing assertiveness in the South China Sea, the loss of the Philippines could be a major headache for US policy planners.
Only month's before Duterte's June swearing in, the two countries inked an agreement granting US military forces access to five bases in the Philippines. It's a major boost for US troops in the Pacific as China has engaged in the development, and by many assessments militarization, of man-made islands in the South China Sea.
In July, an international tribunal in The Hague ruled in favor of the Philippines in a maritime dispute that was seen as a victory by the US, concluding that Beijing had no legal basis to claim the bulk of the South China Sea.
But Duterte has singled that he is willing to enter bilateral negotiations with the Chinese over the dispute and has publicly expressed a desire for closer relations with the Asian power.
Asked about the Philippines' relations with other countries, Toner, the State Department spokesman, said the US was not opposed.
"This is not a zero sum game for us," he said. "We are not trying to dictate with whom the Philippines have a strong relationship with."