For two years since its inception, AI-powered digital assistant Alexa has seen Cortana as stark competition, but that is changing now. Amazon and Microsoft have partnered to closely integrate Cortana with Alexa, giving the e-commerce company instant foothold in about 150 million Cortana-enabled Windows 10 computers, and the Redmond giant will get Cortana on Alexa-enabled devices. The two AI assistants will begin talking to each other later this year, the companies said.

The Microsoft-Amazon partnership will also enable Cortana to work with Alexa on a range of devices, the companies said. Things are going to be a little weird initially. A user would have to say "Cortana, open Alexa," and "Alexa, open Cortana," for instance.

As part of the unusual partnership, Amazon CEO Jeff Bezos to say Alexa will be able to work with Office products, a feature of Cortana that he particularly liked. Office products are popular with over one billion users. Office 365, the subscription-based productivity suite from Microsoft had more than 60 million users as of last year.

Cortana users will be able to use Alexa to shop on Amazon.com and manage their orders, Microsoft said. They will also get access to "Cortana’s world knowledge and helpful productivity features such as calendar management, day at a glance and location-based reminders simply by asking Alexa to open Cortana."

"With Alexa as a guest on Cortana, Cortana users will now have another way of making their lives easier with a great shopping experience. Say you are at work, and you receive a text from your partner saying, 'We're running low on diapers.' In the future, on your Windows 10 PC, iPhone or Android phone, you could simply say, 'Hey Cortana, open Alexa,' and ask Alexa to order diapers using your preferred payment method for your Amazon account," Microsoft said.

"With Cortana as a guest on Alexa, Alexa users will have access to some of Cortana’s most useful productivity capabilities that help people stay organized and on top of what’s important to them. What if you’re making breakfast in the morning and need to know if you have enough time to drop off the dry-cleaning before work? On your Alexa device, you can say, 'Alexa, open Cortana,' and ask when your first meeting is. If you won’t have enough time, simply ask Alexa to open Cortana again and set a reminder for the end of your workday to drop off the clothes," the copmany added.

Amazon is open to the idea of opening Alexa to other competing AI assistants, though it has so far only approached Microsoft, Bezos told The New York Times in an interview. He noted, however, that it remains to be whether Google and Apple, both of which have their own smart speakers as well as digital assistants on their respective mobile operating systems, would be interested. Microsoft and Amazon have worked together in the past. The Echo and Echo Dot smart-speakers are powered by Bing search engine, instead of Google.

Alexa-powered Echo and Echo Dot have significant lead in the smart-speakers market, according to figures from marketing research firms. Unlike Google and Apple, Amazon and Microsoft are the only two companies that have opened their AI-powered digital assistants to be used by third-party companies in their smart-speakers. All four however, have opened access for third parties to serve their customers through the assistants, with SDKs and APIs.

Microsoft and Amazon of course, have their own mobile operating systems as well, but their reach is negligible. Amazon's Alexa, Microsoft's Cortana, and Google's Assistant all have apps for rival operating systems - namely, Android and iOS - but none of them are as capable as the native offerings from Google and Apple respectively.