MANILA (Reuters) - United States Defense Secretary Lloyd Austin said on Tuesday the U.S. alliance with the Philippines would transcend changes in administrations, as he reiterated his support for the Southeast Asian nation.

The Philippines will remain an important country for the United States for many years, Austin told a press conference during a visit to the Philippine military's Western Command on the island of Palawan next to the South China Sea.

Both Austin and Philippine counterpart Gilberto Teodoro expressed concerns over China's conduct in the South China Sea, with the Pentagon chief reiterating Washington's defence commitments to the Philippines under a 1951 Mutual Defense Treaty.

Austin said the treaty would also cover armed attack in the South China Sea, where he said China had used dangerous and escalatory measures to try to assert its expansive claims.

The Philippines and China have been embroiled in repeated spats in the past few years over disputed features within Manila's exclusive economic zone, sparking regional concerns about a miscalculation and escalation at sea.

China claims sovereignty over almost the entire South China Sea, a conduit for more than $3 trillion in annual ship-borne commerce, putting it at odds with its Southeast Asian neighbours.

(Reporting by Manila newsroom; Editing by Martin Petty)