WASHINGTON >> As the body count mounts in the Philippines’ deadly war on drugs, and its combative president’s rhetoric plumbs new depths, the mood in Washington toward a key Asian ally is hardening.

Influential U.S. lawmakers are warning that the extra-judicial killings in the drug war — President Rodrigo Duterte on Friday compared it to the Holocaust — could affect American aid.

And while the Obama administration maintains that its 65-year-old alliance with the Philippines remains “ironclad,” a senior U.S. diplomat is cautioning Duterte against more anti-U.S. posturing.

“I think it would be a serious mistake in a democratic country like the Philippines to underestimate the power of the public’s affinity for the U.S. That’s people power,” Assistant Secretary of State Daniel Russel told The Associated Press.

Russel did not draw a direct comparison, but past Philippine presidents have been toppled by popular protests dubbed “people power,” including former dictator Ferdinand Marcos, who was ousted in 1986.

Duterte has bristled at U.S. criticism of the drug war and repeatedly spoken about dialing back security cooperation — although he says he will maintain the alliance. This week he said that joint military exercises of Filipino and American troops scheduled for next week in the Philippines will be the last such drills.

His foreign secretary quickly said the decision was not final. Such a step would impede Washington’s plans to expand the footprint of U.S. forces in Southeast Asia to counter China.

The previous Philippine government signed an agreement to give the U.S. forces access to five Philippine military bases. That reflected Manila’s anxiety over the territorial ambitions of China with which it has competing claims in the disputed South China Sea.

“If he followed through on this pledge it would be devastating to alliance management,” said Gregory Poling, a fellow with the Southeast Asia program at the Center for Strategic Studies. “How does one sustain a military alliance if your militaries don’t exercise together?”

The Obama administration has consistently played down the significance of such pronouncements from Duterte, which have typically been walked back by other Philippines officials. On Friday, the Philippine leader said that Adolf Hitler had killed 3 million Jews and that he himself would be “happy to slaughter” 3 million addicts. More than 3,000 people have died in the crackdown on drug pushers and users since Duterte took office three months ago.

In Hawaii to meet with Southeast Asian defense ministers, Defense Secretary Ash Carter hinted at U.S. impatience with the Philippine government over Duterte’s remarks. “Just speaking personally for myself, I find these comments deeply troubling,” Carter said. A day earlier, he had described the U.S. relationship with the Philippines as “ironclad.”

The State Department has tended to parry questions about Duterte’s outbursts. Spokesman Mark Toner also described the Holocaust reference as “troubling.” However, Sen. Ben Cardin, top-ranking Democrat on the Senate Foreign Relations Committee, pulled no punches.

“It is reprehensible and, frankly, disgusting that a democratically elected leader is talking about the mass murder of his own people, with Hitler’s Holocaust as his inspiration, no less,” he said.

Cardin and Democratic Sen. Patrick Leahy, author of a law that prohibits U.S. assistance to foreign security forces that commit gross human rights abuses, took to the Senate floor this week to decry the drug war. They accused Duterte of terrorizing Filipinos through his drug war and endorsing “mass murder.”

Leahy, a senior figure on the Senate Appropriations Committee, said because of the “systemic challenges” in the Philippines it may be necessary to consider further conditions on aid until the Duterte government “demonstrates a commitment to the rule of law.”

The aid Manila gets from Washington is substantial — although it may pale next to the investment that could potentially flow from regional economic powerhouse China, where Duterte is expected to visit in October in a bid to improve ties with Beijing.

The Philippines received about $175 million in U.S. development assistance in fiscal 2015 and $50 million in foreign military financing. In 2016, it has gotten $75 million for counterterrorism and maritime security. Since 2011, it has received three decommissioned U.S. Coast Guard cutters to bolster its meager navy.

Russel said Thursday it was no surprise that senior lawmakers were looking to monitor where U.S. assistance funds were going, given the “collateral damage” from the drug war. But he added it’s premature to impose restrictions on aid.

He stressed Washington’s desire to work with Duterte. He said the U.S-Philippine relationship — rooted in a 1951 mutual defense treaty — remains very popular in the Southeast Asian country, notwithstanding Duterte’s repeated references to rights abuses committed a century ago under American colonial rule.

“All politicians have to be responsive to both the mainstream public attitude and the national security and economic interests of their country. All of that leads to continued close ties between our two countries,” Russel said.

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AP National Security Writer Robert Burns in Hawaii contributed to this report.