Private groups in the Philippines are planning a mission to give food, oil and other supplies to fishers in the disputed South China Sea.
Organizers say about 100 fishing boats of various sizes will sail near Scarborough Shoal next week.
China has been stepping up maritime activities in the area, which Manila claims is a traditional fishing ground for Philippine boats.
The coalition group, Atin Ito, told reporters on Wednesday that the vessels will depart on May 15.
The organizers say the voyage is aimed at peacefully asserting the country's sovereignty in the contested waters.
Rafaela David, co-convener of Atin Ito, said: "Through this mission, we seek to send a powerful message to the international community, particularly China. By peacefully but firmly asserting our presence, we demonstrate our unwavering commitment to defend our maritime territory and uphold the rule of law."
Fisherman Leonardo Cuaresma said, "Our heart is overflowing with happiness because this is not just our fight, but also the fight of everyone, of the entire Filipino people."
The coalition attempted a similar voyage in December.
It was believed to have headed near the Second Thomas Shoal, where a Philippine military outpost is located.
But the trip failed after members said they were harassed by the Chinese coast guard and militias.
Tensions are continuing to rise in the South China Sea.
On April 30, Chinese coast guard ships fired water cannons at Philippine vessels near the Scarborough Shoal.