China and the United States have agreed to have their armed forces train to work together for natural disaster and humanitarian missions. Once could say this has already occurred during the current anti-piracy patrol off Somalia, where the United States provides many essential services (although actual command of the task force rotates). The experience off Somalia may have led to this new undertaking.
Meanwhile, in the last decade, China has increased the number of peacekeepers deployed from 100 to 2,000. This makes China one of the top-20 contributors of peacekeeping troops. In addition, there has been a similar increase in cooperation with other nations in counter-terrorism efforts. This is part of Chinas effort to create more rapid reaction forces, so they can intervene in far off crises. An example of this is the arrival, earlier this year, of two Chinese warships (and a supply ship) off the coast of Somalia, to help with the international anti-piracy effort. The Chinese squadron contained a detachment of commandos, who had been trained on how to retake ships from terrorists or pirates.
There's no real mystery to all this. China is getting more involved in peacekeeping and crises intervention simply because its growing economy has customers, and suppliers, all over the world. Most of the peacekeeping and crises are in Africa, and that's where China obtains lots of raw materials, and sells an increasing amount of goods. China, in effect, is taking care of business. Just like any other nation that is fully engaged in the global economy. China has also noticed how America often uses its vast military resources for disaster relief, and gets a prompt boost in popularity for the United States.