China has taken its widening spat with Japan to the United Nations, accusing Tokyo of threatening ¡°an armed intervention¡± over Taiwan and vowing to defend itself in its strongest language yet in the 2-week-old dispute.

Japanese Prime Minister Sanae Takaichi committed ¡°a grave violation of international law¡± and diplomatic norms when she said a Chinese attack on Taiwan could trigger a military response from Tokyo, China¡¯s U.N. Ambassador Fu Cong wrote in a letter on Friday to U.N. Secretary-General Antonio Guterres.

¡°If Japan dares to attempt an armed intervention in the cross-Strait situation, it would be an act of aggression,¡± Fu wrote, according to a statement from China¡¯s U.N. mission. ¡°China will resolutely exercise its right of self-defence under the U.N. Charter and international law and firmly defend its sovereignty and territorial integrity.¡±