China has lashed out after the US secretary of state pledged that his country stands ready to back the Philippines, Beijing’s regional rival.

Antony Blinken promised on Tuesday during a trip to Manila that Washington retains an “ironclad” commitment to defend the Philippines. The United States has been deepening diplomatic and military contacts with its ally recently as tension with China rises.

Beijing promptly responded to the US official’s statement, insisting that the US has “no right” to interfere in the South China Sea, where Beijing and Manila have competing territorial claims.

Tension has risen in recent months, with incidents including a collision between Philippine and Chinese vessels near disputed reefs.

“These waterways are critical to the Phillippines, to its security, to its economy, but they’re also critical to the interests of the region, the United States and the world,” Blinken said at a joint news conference with counterpart Enrique Manalo.

Several countries in the region maintain competing territorial claims to the waters of the South China Sea. China, however, claims almost the entire area.