Can I change my iPad app to be universal in an app update?

I am planning to launch an iPad only app for now. However, I would like to enable iPhone support for the app in one of the updates in future. Is this something Appstore will allow and can I do that by simply making my app Universal in Xcode?
Sure, adding functionality such as your example is encouraged, actually.

If you were wanting to go the other way, and say make a uni-app iphone only down the road, then you'd be facing pushback during review, since you'd be taking something away from that app's ipad users...a no-no.
Can I change my iPad app to be universal in an app update?
 
 
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