Now this is interesting

From Australia's The Age:

China, US swap N Korea secrets
Strategic rivals China and the United States have been secretly sharing intelligence about North Korea.

Leaked records of highly sensitive US-China defence consultations reveal that despite Chinese complaints about US arms sales to Taiwan and American concerns about a growing Chinese espionage threat, the CIA, the US Office of the Director of National Intelligence and the US Defence Department have all held secret discussions on North Korea with Chinese military intelligence.

According to US diplomatic cables obtained by WikiLeaks and provided exclusively to The Age, US-Chinese defence consultative talks held in Beijing in July 2009 included lengthy exchanges about North Korea between US Defence Under Secretary for Policy Michele Flournoy and top-ranking Chinese generals including People's Liberation Army Intelligence Department director Major-General Yang Hui.

In the course of the discussions, General Yang referred to the "close co-operation" between the US and China on "matters of intelligence" concerning North Korea and cited "a recent PLA Intelligence Department visit to exchange information with the CIA".

At the heart of the matter:

Mr Chun said that in the event of a North Korean collapse, China would clearly "not welcome" any US military presence north of the Korean Peninsula demilitarised zone. However, again citing his conversations with Mr Cui and Mr Liu, Mr Chun said China would be comfortable with a reunified Korea controlled by Seoul and anchored to the US in a "benign alliance" - as long as Korea was not hostile towards China.

Works for me. That is going to be one hella big case of culture--shock when the NorK government finally collapses and the citizens actually see what they were being denied.