Not for three decades has rhetoric over border tensions between China and India been so heated. Nationalism is such that a stand-off between troops in disputed territory on a Himalayan plateau could easily escalate. President Xi Jinping and India’s Prime Minister Narendra Modi are in Hamburg for the G20 summit, but the risks necessitate urgent talks on the sidelines. With so much at stake, there is every need for restraint and a return to negotiations. Troops have been building in strength on both sides for a month in the Donglong region, an area neighbouring Tibet claimed by China and the tiny kingdom of Bhutan. Construction of a road by the People’s Liberation Army prompted Bhutan to call on its closest ally, India, for help and soldiers were sent across the border from the Indian state of Sikkim. For New Delhi, the deployment was also protection of a corridor of land that connects India with its northeastern states. China has retaliated by preventing Indian pilgrims from using a nearby pass to visit a sacred Tibetan mountain. China’s Xi Jinping and India’s Narendra Modi meet on G20 sidelines amid simmering border tensions China and India went to war over their disputed 3,500km border in 1962 and India suffered a humiliating defeat. Tensions have since flared from time to time and although talks have made some progress, a final resolution remains elusive. There has been no fighting so far this time, although the shrillness of the rhetoric reveals how bad relations between Beijing and New Delhi have become. India’s army chief has said his country is ready to fight a “two-and-a-half front” war, referring to China, Pakistan and domestic insurgencies, while Chinese officials have warned that in another conflict, the losses would be worse than in 1962. Nationalism and pride are driving such words, but there are also a litany of grievances. China’s strong ties with India’s great rival, Pakistan, have long rankled, but New Delhi now worries China is trying to expand its sphere of influence in South Asia. India has been improving relations with the US, Japan and other Chinese rivals and refused to join Beijing’s “Belt and Road Initiative”. India’s hosting of exiled Tibetan spiritual leader the Dalai Lama has been a major sticking point; his week-long visit in April to the disputed border region of Arunachal Pradesh, known to China as South Tibet, understandably angered Beijing. The difficulty of resolving the border issue has led China to adopt a strategy of building trust through increased trade and investment. It makes sense for the sides to work together; as Asia’s fastest growing large economies and with 35 per cent of the world’s population, they have the potential to drive global growth and development. But strong long-term alliances can only come about if border disputes are settled.