The firm said that the engine is being targeted for next-generation systems and high-end PCs due to an "aggressive" minimum specification.
"I'm sure at some point mobile will be a major consideration, but not the current generation of iOS devices right now," senior technical artist Alan Willer told Digital Spy.
"We're definitely going to be very aggressive about what platforms we put it on, but there's definitely going to be a minimum spec in which, okay, this is our entry level for Unreal Engine 4.
"Unreal Engine 3 is obviously working very well for us on current generation of mobile devices and probably going forward for quite a while."
While Willer said it won't take too long for the engine to release on mobile devices, there is bound to be a "period of overlap" between engines.
"If all we're looking at is support for more rendering features and speed, then UE3 will continue to work on those [devices], you just won't have all the tools that UE4 has," he said.
"Or you can do UE4, and have a set of limits on what you can do, and have access to those tools. I don't know if there's going to be a hard fast, 'You must change over here'."
He added: "For a while it obviously makes sense to just ship using UE3, then we'll sort out what our mobile plans are that will become part of the UE4 suite of abilities."
Epic Games has previously confirmed that the first Unreal Engine 4 games will debut next year, but said it could launch with next generation systems if developers were "horribly aggressive".
Unreal Engine 4 was showcased at this year's E3 Expo, revealing a new real-time video, demonstration and images.
Watch a real-time video of Unreal Engine 4 below:
View images of Unreal Engine 4 below:
Copyright: Epic Games