Duterte has announced plans to scrap 21-year-old agreement with US amid what critics say is a move closer to China.
Senators in the Philippines have launched a Supreme Court challenge against the president scrapping a long-standing defence agreement with the United States.
They argue that President Rodrigo Duterte cannot unilaterally scrap any agreement approved by them.
The Philippines has been one of Washington’s closest allies in Asia for decades and Duterte’s critics fear he is selling out to China.
Al Jazeera’s Jamela Alindogan reports from Manila.