The US navy said on Wednesday that it would dismantle a minesweeper that ran aground on a coral reef in the Philippines after carefully studying all options on how to remove the damaged ship.

The navy spokesman James Stockman said dismantling the USS Guardian was determined to be the solution that would involve the least damage to the Tubbataha Reef, a protected marine sanctuary where the ship got stuck 17 January.

He said the Philippine coastguard was reviewing the plan, but gave no other details.

The navy had said previously that the ship would be lifted by crane on to a barge and taken to a shipyard, but apparently the damage was too extensive and it will have to be cut up and removed in pieces. Stockman gave no time frame for the operation.

The grounding caused no casualties to the ship's 79 crew and officers, who were taken off the vessel after it crashed into the reef in shallow waters. The ship began listing and taking on water through holes in the wooden hull. The navy's support vessels siphoned off remaining fuel and salvage teams removed heavy equipment and hazardous material.

The navy is investigating the incident, which caused Philippine government agencies and environmentalists to express concern about the extent of damage to the coral reef.

Philippine President Benigno Aquino III said last week that the US navy must explain how the ship got off course. He said the navy would face fines for damaging the environment.

Thomas Carney, commander of the navy's Logistics Group in the Western Pacific, told reporters last week that the investigation would look into all the factors that may have led to the grounding, including a reported faulty digital chart, sea conditions, weather and the state of the ship's navigational equipment.

The navy and the US ambassador to the Philippines, Harry K Thomas, have apologised for the grounding and promised to co-operate with its close ally.