The US Navy says faulty navigational charts may have caused its warship to run aground on a world heritage reef in the Philippines.

The minesweeper USS Guardian grounded itself on the Philippines' Tubbataha Reef on Wednesday night.

The US Navy has told its Pacific Fleet ships of an error in its navigational chart on the location of the reef and says this may be a factor in the accident.

A US team has been working for the past three days to try to free the warship with the least environmental damage to the UNESCO World Heritage site.

Both US and Philippines authorities admit the incident could have damaged at least 10 metres of the coral reef which sits in a marine protected park and is one of the most biologically diverse areas in the Coral Triangle.

Philippines senators say they want an inquiry into the incident to uncover possible violations of Philippines and international laws.