China and US have reasons to cooperate in Afghanistan

Chinese Vice President Li Yuanchao and Afghan President Mohammad Ashraf Ghani attend a reception marking the 60th anniversary of China-Afghanistan diplomatic ties in Kabul, Afghanistan, on Nov. 3, 2015.
The first round of the four-party talks on Afghanistan held in Islamabad on Monday saw Afghanistan, Pakistan, China and the United States discussing a peace road map for the Afghan government and the Taliban.
But why are China and the US cooperating to resolve Afghanistan’s problem?