BEIJING — Apple is facing a potential setback in China, one of its biggest and fastest-growing markets, after the much-anticipated introductions here of the new iPhone models were delayed.

On Wednesday, Apple told China’s three big state-owned mobile service providers that it would not release the iPhone 6 and iPhone 6 Plus in mainland China on Sept. 19, when sales start elsewhere. The carriers had already booked advertising campaigns for the phones.

The move set off consternation among Apple’s partners in China, as well as with consumers who had been eagerly awaiting the introductions. Apple did not explain the delay, executives at the carriers said, but it appeared the phones had not received approval from Chinese regulators to go on sale.

The Chinese leadership and the state-controlled news media grew wary of foreign technology providers after revelations last year by Edward J. Snowden of American cyberspying. In July, CCTV, the main state-controlled television network, broadcast a report saying that the iPhone could represent a threat to China’s national security. The accusations were promptly rejected by Apple.