Apple iPad Air 2
Apple CEO Tim Cook holds an iPad during a presentation at Apple headquarters in Cupertino, California, Oct. 16, 2014. Reuters

Apple is planning on more than doubling its number of retail stores in Greater China from 15 to 40 over the next two years, CEO Tim Cook announced while on a trip to the country Thursday. Cook also said that China, which has been slower to accept products such as the iPhone and iPad than Western countries, will “become Apple's biggest revenue contributor.”

The Cupertino, California-based company opened its first Chinese retail store in Beijing in 2008. Since then, Apple has expanded with retail outlets in Shanghai, Chengdu, Chongqing, Wuxi, Shenzhen and Hong Kong, as well as other stores in Beijing. Hong Kong and Taiwan are also included in Greater China, which contributed to 14 percent of Apple revenue ($5.8 billion) in the three months ending on Sept. 27, according to Bloomberg.

“It's just a matter of time” before China generates more revenue than other nations, Cook said Thursday. His remarks were first published and translated by Sina Corporation, a Chinese media outlet. Chief Financial Officer Luca Maestri also said earlier this month that demand in the country of nearly 1.4 billion people has “been really off the charts.”

While overseas Cook also met with Chinese Vice Premier Ma Kai to discuss increased security around user data and visited a Foxconn technology plant where the iPhone 6 is made in Zhengzhou, located in northern central China.

The iPhone 6 and iPhone 6 Plus first became available in China on Oct.r 17 after selling more than 39 million iPhones during the quarter before. Cook previously hinted that more investment in China would be coming sooner than later, saying during a call with investors that the company is still teaming up with phone carriers there.

“Demand for the new iPhones has been staggering,” Cook said, as quoted by the New York Times. “I've never felt so great after a launch.”