China claims around 90,000 square kilometers (35,000 square miles) of land in India's northeastern state of Arunachal Pradesh, while India says China is occupying 38,000 square kilometers (15,000 square miles) of territory on the Aksai Chin plateau in the western Himalayas.
The two nations face tensions in other areas as well. China is a longtime ally and weapons supplier to Pakistan, India's bitter rival. The presence in India of the Tibetan spiritual leader the Dalai Lama and the self-declared Tibetan government-in-exile irks Beijing. China is also suspicious of New Delhi's growing ties with the United States.
Despite the tensions, trade between India and China has soared, with China becoming India's biggest trading partner. Two-way trade jumped from $5 billion in 2002 to nearly $75 billion in 2011, but declined slightly last year because of global economic conditions.
India is concerned, however, that trade remains heavily skewed in China's favor.