After the US ambassador to India Richard Verma went to Tawang in Arunachal which abuts Chinese border, Beijing said such acts will make the dispute more "complicated" between the two countries and "sabotage" peace in the region.
"You have also noted that the place visited by the senior diplomatic official is disputed region between China and India. We are firmly opposed to the visit to the disputed area between India and China," Chinese Foreign Ministry spokesperson Lu Kang said at a regular media briefing.
China claims a huge chunk of India's northeast state Arunachal Pradesh, which it calls as South Tibet. Verma visited Tawang to attend a festival.
"It will only make the dispute more complicated, disturb peace and tranquillity of border areas and sabotage the peaceful development of the region," Lu said.
"We urge the US to stop interference in boundary issue between China and India and make more commitment to regional peace and stability."
Lu said the boundary issue between India and China was complex and sensitive and interference by a third party would heighten tension.
Lu maintained that China's position on the eastern sector was "clear and consistent".
"Two countries are now trying to resolve territorial disputes through negotiations and consultation. Any third party should have sense of responsibility and should respect efforts made by China and India for peace reconciliation and tranquillity rather than opposite.
"Behaviour of the US runs contrast to efforts by China and India," Lu said.
"At the end of the day, only the peoples of the two countries will fall victim. We believe India and China have the wisdom to properly handle the dispute," he added.