The Philippines on Tuesday said the deployment of US spy planes, suggested by President Benigno Aquino, was just one option to monitor the country's territory, as China appealed for stability in the region.
"If they happen at all, they are surveillance flights, they are not meant to be provocative. There's no offensive capability here," said the president's spokesman Ricky Carandang.
China's foreign ministry, in an embassy statement quoting spokesman Liu Weimin, called on all parties to maintain "peace and stability" in the South China Sea.
"We have noticed the reports," the ministry spokesman was quoted as saying.
"It is the hope of the Chinese side that peace and stability can be maintained... and parties concerned do things conducive to regional peace and stability," the statement said.
It did not specify the Philippines or the United States or mention the almost-three month long dispute between China and the Philippines over the Scarborough Shoal in the South China Sea.
The Scarborough Shoal dispute began after Chinese government vessels blocked Philippine ships from arresting Chinese fishermen near the shoal on April 10.
Both countries have been pressing their respective claims to the area with the poorly-equipped Philippines seeking the support of its main defence ally, the United States.
China claims nearly all of the South China Sea, even waters close to the coasts of neighbouring countries. The Philippines says the shoal is well within its 200-nautical-mile exclusive economic zone.
The shoal sits about 230 kilometres (140 miles) from the western coast of the Philippines' main island of Luzon. The nearest major Chinese land mass is 1,200 kilometres northwest of the shoal, according to Philippine navy maps.