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The State Department halted the planned sale of some 26,000 assault rifles to the Philippines' national police after Senator Ben Cardin said he would oppose it amid concerns about human rights violations, Senate aides told Reuters.

Aides said Cardin, the top Democrat on the U.S. Senate Foreign Relations Committee, was reluctant for the United States to provide the weapons following criticism of president Rodrigo Duterte's deadly battle to rid the country of drugs.

A protester shouts after scuffling with riot police near the U.S. Embassy during a rally Friday. Aaron Favila / AP

News of the move was met with disappointment in Manila. Police spokesman Dionardo Carlos said the Philippines had yet to be notified about the sale being stopped.

The relationship between the United States and the Philippines, a long-time ally, has been complicated lately by Duterte's angry reaction to criticism from Washington.

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More than 2,300 people have been killed in police operations or by suspected vigilantes in connection with the anti-narcotics campaign since Duterte took office on June 30.

The State Department informs Congress when international weapons sales are in the works. Aides said Foreign Relations committee staff informed State that Cardin would oppose the deal during the department's prenotification process for the sale of 26,000-27,000 assault rifles, stopping the deal.

Related: U.S. 'Baffled' by Philippines Split

U.S. State Department officials did not comment.

Ronald dela Rosa, the Philippine national police chief and staunch supporter of the war on drugs, said he liked the American rifle, but suggested China as an alternative small-arms provider.

"We really wanted the U.S. rifles because these are reliable," he told broadcaster ABS-CBN.

"But if the sale will not push through, we will find another source, maybe from China."

In October, Duterte told President Barack Obama to "go to hell" and said the United States had refused to sell some weapons to his country, but he did not care because Russia and China were willing suppliers.

According to some U.S. officials, Washington has been doing its best to ignore Duterte's rhetoric and not provide him with a pretext for more outbursts.

Photos: Philippines' Deadly Drug War

An open break with the Philippines could create problems for the United States in a region where China's influence has grown.