It is obviously now! If you want the proof of that, Pakistan should try doing something that Chinese do not like. They will come down on you like a ton of bricks. You saw the proof of that in Kargil conflict. Here is a quote:
On June 12, 1999, when the Pakistan Foreign Minister Mr. Sartaz Aziz went to Beijing to seek Chinese support, China told Pakistan to settle its disputes with India peacefully through dialogue and negotiations.
Reasons behind China* 's neutrality *
C*hina’s views on Kargil has to be seen in the broader context of its policy on Kashmir . In the last two decades, there has been a change in its Kashmir policy, which has much to do with its own internal compulsions. During the days of Sino-Indian hostility, China adopted a pro-Pak policy on Kashmir , and talked of the right to self-determination of the Kashmiri people. By the early 1980s, however, the new thinking in China developed an anathema for the word self-determinationlest it be applied by the West to the case of Tibet . The rise of secessionist tendencies in its Muslim province of Xinjiang also made China aware of the dangers of self-determination. Moreover, by the late 1980s, China 's own territorial disputes with the South-East Asian countries over the Spratly Group of Islands led to military clashes. Having shown its preference for bilateral talks to resolve the dispute, China could not deny the same principle in the case of Kashmir . Therefore, as relations between India and China improved by the end of the 1980s, China advocated bilateral talks between India and Pakistan on Kashmir . In fact, during his visit to India and Pakistan in December 1996, the Chinese President, Mr. Jiang Zemin, stunned the Pakistani Senate by calling on both countries to build a co-operative relationship and set aside difficult issues. Although he did not directly mention Kashmir the reference was obvious. *
There are other reasons why China cannot support Pakistan on Kashmir or Kargil. The very foundation of Pakistan is based on Islam and therefore is a source of religious terrorism. While it has openly supported terrorist forces in Kashmir , there are reports of Uighur Muslim terrorists getting training in Pakistani camps. In fact, China had protested to Pakistan on this issue in February this year, an allegation denied by Pakistan . Besides, after the break-up of the Soviet Union , Muslim fundamentalism is on the increase in Central Asia . Any support to Pakistan on Kashmir , therefore, will only lead to more problems in the adjoining more vulnerable Chinese province of Xinjiang .
Articles #211 , Chinese Views on the Kargil Conflict
As a direct result of Chinese demand, Pakistan stopped supporting Uighur muslims in China. So your statement is patently false.