Pakistan has been ‘occupied’ by the United States for the purpose of invading Iran among other things. Pakistan would be the base for mounting massive air reconnaissance and surveillance of Iran. #msg-3483139
For the United States to use Pakistan, a country that borders China, as a base will never do.
In a countermove China is taking measures to secure major influence over Pakistan and thus prevent the likelihood of the U.S. using Pakistan as a base.
Moreover China has just welcomed Pakistan's inclusion in ARF and China has also assured its support to Pakistan for joining the Shangahi Cooperation Orgnaizaton (SCO). http://www.paknews.com/top.php?id=1&date1=2004-04-10