Apple has announced that its latest smartphone, the iPhone 4S, will finally launch in China and 21 additional countries Friday, January 13th. After this rollout, the iPhone 4S will be available in 90 countries.

China Unicom has been the only official iPhone partner in China in the past, and Apple has made no announcement that it will be expanding to China Mobile, the world’s largest carrier.

“Customer response to our products in China has been off the charts,” said Tim Cook, Apple’s CEO. “With the launch in China next week, iPhone 4S will be available in over 90 countries making this our fastest iPhone rollout ever.”

On January 13, the iPhone 4S will be available in  Anguilla, Antigua and Barbuda, Bolivia, Botswana, British Virgin Islands, Cameroon, Cayman Islands, Central African Republic, China, Dominica, Dominican Republic, Ecuador, Grenada, Guam, Guinea Conakry, Ivory Coast, Jamaica, Kenya, Madagascar, Mali, Mauritius, Niger, Senegal, St. Vincent and The Grenadines, Trinidad and Tobago, Turks and Caicos and Uganda.

Apple will hold its financial earnings call for the 2011 holiday season on January, 24th. The company has shown continued growth in China each quarter. Tim Cook famously said during the last earnings call that, when it comes to China, “the sky is the limit.”