In 1949, China closed the border between Nubra and Xinjiang, blocking old trade routes. In 1955 China began to build roads connecting Xinjiang and Tibet through the Aksai Chin area. The Indian effort to retain control of Aksai Chin led to the Sino-Indian War of 1962, which India lost. China also built the Karakoram highway jointly with Pakistan. India built the Srinagar-Leh Highway during this period, cutting the journey time between Srinagar and Leh from 16 days to two. The route, however, remains closed during the winter months due to heavy snowfall. Construction of a tunnel across Zoji La pass is under consideration to make the route functional throughout the year.