China admonished the United States today for sending its ambassador in India to a contested stretch of land on the India-China border, warning that a third party's meddling would only complicate the dispute between Beijing and New Delhi.

China claims more than 90,000 sq km (35,000 sq miles) of territory disputed by India in the eastern sector of the Himalayas. Much of that forms the Indian state of Arunachal Pradesh, which China calls South Tibet.

US Ambassador to India Richard Verma posted photos on his Twitter account on October 21 of his recent trip to Arunachal Pradesh, thanking Indian officials for their "warm hospitality" and calling the region a "magical place".

Chinese Foreign Ministry spokesman Lu Kang said China was "firmly opposed" to the US diplomat's actions, which he said would "damage the hard-earned peace and tranquillity of the China-India border region".

"Any responsible third party should respect efforts by China and India to seek peaceful and stable reconciliation, and not the opposite," Lu told a regular press briefing.

"We urge the United States to stop getting involved in the China-India territorial dispute and do more to benefit this region's peace and tranquillity," he said, adding that China and India were handling the matter appropriately through talks.

India's Ministry of External Affairs described Verma's visit as "nothing unusual".

"The US Ambassador visited Arunachal Pradesh, a state which is an integral part of the country to which he is accredited," MEA spokesman Vikas Swarup said in response to the Chinese statement.

No comment was available from the US Embassy in New Delhi.

Disagreement between nuclear-armed China and India over parts of their 3,500-km (2,175-mile) border led to a brief war in 1962. The countries have moved to control the dispute, but repeated rounds of talks have failed to make much progress.

India says China occupies 38,000 square km (14,600 sq miles) of its territory on the Aksai Chin plateau in the west, and is also suspicious of China's support for its arch-rival, Pakistan.

Tensions occasionally flare over the disputed border. In August, China was angered by India's plans to place advanced cruise missiles there.