Apple's CEO Tim Cook has penned an apology to Chinese consumers over warranty and after-sales issues in China.

On March 15, World Consumer Rights Day, Chinese television ran stories about Apple's poor warranty policies in China and how they fell short of similar Apple policies in other countries. To make matters worse, Chinese celebrities were apparently asked to post disparaging comments about Apple on social networking microblog site Weibo.com.

In Cook's letter, he assured consumers the company would improve its repair policy for the iPhone 4 and iPhone 4S.

Apple has historically had a difficult time in China. It had barely a presence here until the iPhone was launched, and the company's previous CEO Steve Jobs never made a trip to the nation. In recent years, Apple's manufacturing in China has come under scrutiny as partner Foxconn has witnessed employee suicides and poor internal controls, and Apple's own retail outlets in China have been the scenes of fights and cordoned police barriers.