The Philippines said Sunday it remained locked in a stalemate with China over a disputed shoal in the South China Sea.
The statement came a day after the Philippine side reported that two Chinese vessels remained in Scarborough Shoal, just as the week-old standoff appeared to have eased.
Eight Chinese fishing vessels which sparked the standoff however had already left the area.
"The stalemate remains. Both sides are in touch with each other," Department of Foreign Affairs spokesman Raul Hernandez said in a brief statement.
He said Foreign Secretary Albert del Rosario left Sunday for a week-long trip to the United States, and negotiations would be taken over by one of his top aides.
On Monday, the Philippines and the United States are due to begin joint annual war games to boost its military alliance amid fears of China's growing power in the region.
Local military officials said some of the manoeuvres would take place off the southwestern island of Palawan close to the disputed South China Waters, but sought to downplay fears they could further add to the Scarborough tension.
"The Balikatan (shoulder to shoulder) exercises is in no way related to an event like that of the Scarborough Shoal," said Major Emmanuel Garcia, spokesman for the Philippine contingent.
"We had long planned for this and the focus would be on improving security, counter terrorism and humanitarian and disaster response."
Presidential spokeswoman Abigail Valte said in a statement the government hoped China would not be be alarmed by the exercises.
"We are hoping that this will not result in provocation," Valte said.
She said that while Manila maintained jurisdiction over the shoal, it remained committed to resolving the issue in a diplomatic manner.
The Scarborough Shoal dispute started on April 8 when the Philippines found the eight Chinese fishing boats in the area, which the Philippines claims as its territory.
A Philippine navy warship was deployed there to arrest the Chinese fishermen for illegal poaching, but China sent three civilian surveillance vessels and took turns blocking the ship.
Manila pulled back the naval warship from the area on Thursday and the tension further eased Saturday after the Chinese fishing vessels laden with their catch and escorted by two surveillance ships had already left the area.
But as the Philippines prepared to welcome the positive development, it subsequently reported Beijing had sent back one of the two maritime vessels and a Chinese aircraft made flybys above the lone Philippine vessel.
Manila also said the Chinese harassed a Philippine-registered vessel conducting a scientific survey.
Among those aboard the vessel were nine French citizens helping to conduct an "archaeological survey" in the area, though the foreign department did not elaborate further.
The military has said a Philippine coast guard vessel remains near the shoal, about 230 kilometres (140 miles) west of the country's main island of Luzon, monitoring Chinese activity.