Microsoft is seeking a limited number of people to test "an early version" of its Cortana for iOS app.
Microsoft plans to start sending out download links via email to those approved "in the coming weeks." Testers at the start must be in the U.S.
Cortana for iOS is only available for now in the U.S. and China.
Microsoft officials tipped their hand that Cortana was coming to iOS and Android in the fall of 2014. In May 2015, officials said the Cortana app for iOS would be available before the end of 2015.
Microsoft officials have said that the Cortana apps for iOS and Android won't be as feature-rich as Cortana on Windows and Windows Phone, as it won't be as tightly integrated with the operating system. For example, on iOS, the "Hey Cortana" wake-up feature won't be available, at least not initially.
Microsoft also is integrating Cortana into Xbox One, and is expected to make Cortana available as an integrated component of the coming Cyanogen Android distribution.
Microsoft released the public beta of its Cortana app for Androidin August for U.S. testers.