China lashed out at the U.S. on Wednesday after a pair of B-52 bombers flew past a Chinese-held shoal in the South China Sea, amid escalating words and displays of military strength from the two major Pacific powers.

Foreign Ministry spokeswoman Hua Chunying warned the U.S. against “hyping up militarization and stirring up trouble,” while promising that China would take all necessary measures to defend its sovereignty.

The U.S. “doing whatever they want is risky and China will not be threatened by any military warships,” Hua told reporters at a daily briefing in Beijing.