In late 1967, there were two more conflicts between Indian and Chinese forces at their contested border, in Sikkim, known as the Nathu La and Cho La clashes. Both sides suffered heavy casualties but India came out in a better position than PRC. Between 1967 and 1971, an all-weather road was built across the Aksai Chin territory claimed by India, linking PRC's Xinjiang Uyghur Autonomous Region with Pakistan.The PRC continued an active propaganda campaign against India and supplied ideological, financial and other assistance to dissident groups, especially to tribes in northeastern India. The PRC accused India of assisting the Khampa rebels in Tibet. Sri Lanka played the role of chief negotiator for the withdrawal of Chinese troops from the Indian territory. Both countries agreed to Colombo's proposals. 1970s In August 1971, India signed its Treaty of Peace, Friendship, and Co-operation with the Soviet Union. The PRC sided with Pakistan in its December 1971 war with India. Although China strongly condemned India, it did not carry out its veiled threat to intervene on Pakistan's behalf. By this time, the PRC had replaced the Republic of China in the UN where its representatives denounced India as being a "tool of Soviet expansionism." India and the PRC renewed efforts to improve relations after Indian Prime Minister Indira Gandhi's Congress party lost the 1977 elections to Morarji Desai's Janata Party. In 1978, the Indian Minister of External Affairs Atal Bihari Vajpayee made a landmark visit to Beijing, and both countries officially re-established diplomatic relations in 1979. The PRC modified its pro-Pakistan stand on Kashmir and appeared willing to remain silent on India's absorption of Sikkim and its special advisory relationship with Bhutan. The PRC's leaders agreed to discuss the boundary issue, India's priority, as the first step to a broadening of relations. The two countries hosted each other's news agencies, and Mount Kailash and Mansarowar Lake in Tibet, the home of the Hindu pantheon, were opened to annual pilgrimages. 1980s In 1981, the Minister of Foreign Affairs of the People's Republic of China, Huang Hua made a landmark visit to New Delhi. PRC Premier Zhao Ziyang concurrently toured Pakistan, Nepal, and Bangladesh. In 1980, Indian Prime Minister Indira Gandhi approved a plan to upgrade the deployment of forces around the Line of Actual Control. India also undertook infrastructural development in disputed areas. In 1984, squads of Indian soldiers began actively patrolling the Sumdorong Chu