NATCO offers passenger road service between Islamabad, Gilgit and Sost (near the Chinese border). There is passenger road service between Tashkurgan and the Pakistani cities of Sust and Gilgit. Road service between Kashgar and Gilgit (via Tashkurgan and Sust) started in summer 2006. However, the border crossing between China and Pakistan at Khunjerab Pass (the highest border in the world) is open only between May 1 and December 31 as the roads are blocked by snow during winter.