Philippine President Rodrigo Duterte chided the United States on Wednesday for halting the planned sale of 26,000 rifles to his country, calling those behind the decision "fools" and "monkeys" and indicating he might turn to Russia and China instead.

Duterte's tirades against the former colonial power are routine during his speeches and he said on Wednesday he once believed in Washington, but had since lost respect for the Philippines' biggest ally.

In Washington, U.S. State Department spokesman John Kirby said he regarded Duterte's latest salvo as "inexplicably at odds with the close relationship that we continue to have with not just the Filipino people, but the Filipino government."

The State Department halted the sale of the assault rifles to the Philippine police after staff from U.S. Senator Ben Cardin's office said he would oppose it, Senate aides told Reuters on Monday.

Aides said Cardin, the top Democrat on the U.S. Senate Foreign Relations Committee, was reluctant for the United States to provide the weapons given concern about human rights violations in the Philippines during Duterte's bloody, four-month-old war on drugs.

"Look at these monkeys, the 26,000 firearms we wanted to buy, they don't want to sell," Duterte said during a televised speech.

"Son of a bitch, we have many homemade guns here. These American fools."

More than 2,300 people have been killed in police operations or by suspected vigilantes as part of Duterte's anti-narcotics effort, which was the linchpin of his election campaign.

Duterte has vented his anger at the United States for raising concerns about the extrajudicial killings.

"That's why I was rude at them, because they were rude at me," he said.

According to procedures in Washington, the State Department informs Congress when international weapons sales are in the works. Aides said the State Department had been informed Cardin would oppose the deal during the prenotification process, thus effectively halting the sale.

"Committee staff told State that Cardin would block it if it was sent forward. They haven't sent it. Does that mean it has been stopped? I guess that depends on your definition. It would be highly unusual for State to move it forward with explicit opposition," a Senate aide said on Wednesday.

COMMITTED TO PHILIPPINES ALLIANCE

Kirby, the State Department spokesman, said he was barred from commenting on the status of the sale, while stressing the U.S. commitment to the U.S.-Philippines alliance.

Asked how the United States could have a close relationship with the Phiippines' government without also having such ties with its president, Kirby said in a democracy, the government "doesn't rest on the shoulders of just one individual."

Kirby denied Washington had any plan to circumvent Duterte but rather to stress that it has long and robust relationships with other parts of the government.

"Those are solid, they remain. But obviously, you also need to develop a good working relationship with the head of state," Kirby said. "We're committed to doing that."

Speaking with troops at Fort Leonard Wood in Missouri, U.S. Defense Secretary Ash Carter said the long-standing military alliance had benefited both nations.