Apple COO Tim Cook was reportedly paid a secret visit to China Mobile yesterday. China Mobile is the largest mobile operator in China which was rumored several times to talk with Apple about the iPhone joint force. But no matter how, Apple ended up choosing China Unicom over other players like China Mobile and China Telecom as iPhone cooperator.

Although neither Apple nor China Mobile disclosed the reason why Tim Cook showed up in the largest Chinese mobile operator’s office, but speculations are swirling about Tim Cook came here to negotiate about the introduction of iPhone 4S or the prospective TD-LTE iPhone by China Mobile. China Mobile confirmed such talks are still under negotiation, but haven’t disclose any updates.

Although China Unicom won over Apple to become the exclusive iPhone cooperator in China, but once a while there were rumors about China Mobile in talks with Apple with an aim of introducing something such as new version of iPhone or iPad. And the rumors were spurred by China Mobile head Wang Jianzhou’s remarks of “will continue to seek for the iPhone cooperation opportunity”.

Actually, there’re more than 5 million iPhone users using China Mobile’s wireless network, about the same number as contract iPhone users of China Unicom, which impressed many telecom observers and experts. Given on the big numbers there’s no reason for China Mobile to quit on iPhone.