Reuters: India has seen China as a military threat since its defeat in a 1962 war, but with both emerging as uneven economic powers, New Delhi now fears Beijing will use its massive clout to block its global ambitions.
Here is a list of issues that bedevil ties as Chinese Premier Wen Jiabao arrives in India on Wednesday for a 2-day trip.
ECONOMIC RIVALRY
China and India are scouring the globe -- from Asia to Africa and Latin America -- to secure resources and food supplies to keep powering their burgeoning economies, a rivalry that is partly reshaping global business systems and foreign policy priorities.
India is playing catch-up, trying to chip away at China's decade-long head start in the race for resources. It trails China, for instance, in Africa where Beijing's investments in one country alone, Ghana, topped the entire Indian investment in the continent in 2006.
TRADE
Despite decades of mistrust stemming in part from their territorial rivalry, trade is booming and China is now India's biggest trade partner. The value of bilateral deals is expected to pass $60 billion next year, a 30-fold increase since 2000, raising the stakes in maintaining peace. But the balance of trade is heavily in China's favour. India's trade deficit with China rose from $1 billion in 2001-2 to $16 billion in 2007-8, according to Indian central bank data.
No other country has initiated more anti-dumping investigations with the World Trade Organisation against China than India.
India has sought to diversify its trade basket, but raw materials and other low-end commodities such as iron ore still make up about 60 percent of India's exports to China. By contrast, high-value manufactured goods form the bulk of Chinese exports.
As an example of how India is still heavily dependent on Chinese equipment, Chinese power equipment maker Shanghai Electric Group Co. in late October agreed to sell power equipment and related service contracts worth $8.29 billion to India's Reliance Power over a 10-year period.
BORDER DISPUTE
While a new war is very unlikely, the unsettled border between the world's two most populous countries remains the biggest single impediment to better relations.
The Asian giants still claim vast swathes of each other's territories along their 3,500 km (2,173 mile) Himalayan border which has largely remained peaceful since a border war in 1962.
The border was never demarcated. In the years before Indian independence in 1947, the former British colonial rulers saw little need to demarcate such a remote area and later the two sides were unable to agree on a common border.
India also says Beijing is illegally holding 5,180 sq km of northern Kashmir ceded to it by Pakistan in 1963.
China claims 90,000 square km on the eastern sector of the border. Historians have said China's claim on the eastern sector was to use as a bargaining chip in order to keep control of the strategically important region Aksai Chin.
DALAI LAMA
Beijing's longest running grudge with India is over its granting of asylum to Tibetan leader Dalai Lama, who fled to India in the 1950s following a failed uprising, setting off a chain of events that eventually led to the war between India and China. Beijing, which brands the Dalai Lama a separatist, worries that Tibet's spiritual leader is using his base in the northern hill town of Dharamsala to keep separatist fires alive.
Last year, China reacted angrily to New Delhi's decision to allow the Dalai Lama to visit the border state of Arunachal Pradesh disputed by China. For the first time in years, it also criticised a visit by Prime Minister Singh to the state, suggesting it was raising the stakes there.
The Dalai Lama is due to visit Sikkim, an Indian state on the Chinese border, during Wen's visit, something that could inflame tensions.
DIPLOMACY
Tensions between Asia's two rising powers have simmered since their border war in 1962, but in recent years Beijing and New Delhi have mostly managed to compartmentalise their differences.
The relationship has matured to the point that while they can jointly advocate for the interests of emerging economies through forums such as the Group of 20 and climate talks, India has the confidence to criticise Beijing's currency policy.
Still, India remains deeply wary of its bigger and more powerful neighbour. China, a long-time ally of India's bitter rival Pakistan, is feared to be encircling India in a "string of pearls" by investing in its neighbours such as Sri Lanka and Myanmar. Navy officials say increasing numbers of Chinese ships are sailing just outside Indian waters, and the two still spar over their disputed Himalayan border.
A Chinese decision to provide stapled visas to residents of the disputed Indian Kashmir region has ruffled New Delhi which bristled at any suggestion that the Himalayan province also claimed by Pakistan is not its territory.