American forces took three bells from the Catholic church of Balangiga town in 1901 as war booty in what historians said was a particularly brutal military operation in the former US colony.

The US embassy in Manila announced earlier this month it would send them back but gave no timetable for their return, following a public campaign by Philippine President Rodrigo Duterte.

But reports that some US legislators would oppose the move prompted Philippine Defence Secretary Delfin Lorenzana to join calls for the bells to be brought home.

"We call on the American people not to allow the bells to serve as trophies for atrocities that were committed by both sides on Philippine soil a very long time ago," he said in a statement.

"The return of the Balangiga Bells will be a strong indicator of the sincerity of the Americans in forging a lasting relationship with the Filipino people."

Duterte has demanded Washington give back the Balangiga bells during public tirades against Washington as he builds closer ties with China and Russia.

The president urged their return during his State of the Nation address last year: "Give us back those Balangiga bells. They are not yours. They are ours. They belong to the Philippines. They are part of our national heritage."

Two of the bells are installed at a memorial for US war dead in the state of Wyoming, while the third is with US forces in South Korea.

The Philippines, a Spanish colony for centuries, was ceded to the US in 1898 at the end of the Spanish-American War. The country gained independence from Washington in 1946.

The bells were taken during the brutal Samar campaign, which was launched about a month after Filipino rebels killed 34 US troops in Balangiga on September 28, 1901, according to the US Army War College.