"This is a watershed day," said Cook, who is in Beijing ahead of Friday's launch. He referred to China Mobile as a great cellphone firm with a "very fast network."
"It's a huge announcement...we're incredibly impressed with them, we have deep respect for them," Cook said. "We see this as bringing the world's best smartphone to the very largest and now the fastest network in China."
Cook said that the company sold more iPhones last quarter in Greater China than ever before, and sees this deal as "continuing momentum" that has been building up over the last three or four years. "It really is a key market for us," he said.
Neither Apple nor China Mobile had an exact sales estimates for the iPhone. Industry analysts have been keenly watching for a sales figure. CNBC has learned China Mobile has received 1.2 million pre-orders.
Shebly Seyrafi, an analyst at FBN Securities predicted after the announcement in December that Apple would sell an incremental 17 million units to China Mobile, on top of the roughly 42 million China Mobile subscribers that already use the iPhone.
(Read more: Biggest loser of Apple-China Mobile deal: Samsung)
The deal with China Mobile means that the iPhone will now be available through all state-run telecom carriers in China, home to the world's biggest population and a growing class of consumers.
The two latest iPhones have been sold by rivals China Unicom and China Telecom since they were launched last year. Both firms have trimmed contract prices for the iPhone to keep existing customers and tempt new ones away from China Mobile, according to media reports.
China Mobile said it was not releasing details of subsidies, which will be released with its annual results in March.