Philippine President Ferdinand Marcos Jr. left Wednesday for Washington for the historic trilateral summit with his Japanese and US counterparts.
In his departure address in Manila, Marcos expressed hope the three countries will further strengthen their maritime security cooperation in the South China Sea.
Thursday's meeting will take place amid rising tensions in the waters between the Philippines and China.
On Tuesday in Manila, nearly 100 demonstrators marched toward the Chinese consulate.
They condemned Chinese coast guards for repeatedly firing water cannons at Philippine boats near the Second Thomas Shoal. Those incidents resulted in the injuries of some Filipino soldiers.
The protesters demanded China stop its maritime aggression.
Beijing and Manila have overlapping claims over the area. China says it opposes "stoking bloc confrontation" in the disputed waters.