The Philippines may ask the United States to send spy planes to help it monitor a disputed area in the South China Sea, a presidential spokesman said Monday, in a move that could deepen tensions with China.

The move to request P3C Orion spy planes would first require the approval of President Benigno Aquino's top defence advisers, Ramon Carandang said.

The request "is a possibility as a way to enhance our monitoring capabilities," Carandang told AFP.

"But definitely, this is just for monitoring and surveillance purposes."

The statement comes two weeks after Aquino withdrew a coast guard ship and a fisheries bureau boat that were engaged in a tense stand off with Chinese ships in Scarborough Shoal, a group of rocky outcrops in the South China Sea.

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.

China had welcomed the pull-out, and reciprocated by removing its boats in the area, though both sides have said there was no accord to permanently abandon the area.

Carandang said the request for US spy planes should not be viewed by China as a form of aggression, and sought to downplay fears it could re-ignite tensions in the area.

"It is not inconsistent with our policy to de-escalate tensions in the area. First of all, it is only for surveillance and there is no armed component" to the request, he said.

US State Department spokeswoman Victoria Nuland refused to comment specifically but said that "as part of our long-standing cooperation, the United States supports the Philippines in enhancing its maritime awareness".

Chinese embassy officials were not immediately available for comment, but Beijing has in the past repeatedly warned against US involvement in the dispute.

Last week, China said it would oppose any military provocation in the South China Sea, which it called its "indisputable territory".

That warning was apparently directed at the US, which had recently launched major naval exercises in Hawaii involving 22 nations.

The Scarborough Shoal dispute began after Chinese government vessels blocked Philippine ships from arresting Chinese fishermen near the shoal on April 10.

Since then, both countries have maintained ships there to press their respective claims to the area.

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.

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