Minecraft Earth was announced in May, when the seminal building game celebrated its tenth anniversary.
As well as the ability to build in AR, Minecraft Earth features a location-based game in which players can gather resources and discover mobs as they travel the real world.
The early access version features Adventures, which are procedurally generated, limited-time Minecraft worlds that can be played in augmented reality in life size.
Microsoft says it plans to add more countries each week until Earth is available worldwide by the end of the year.
“This will allow us to have people play, test and provide feedback on the game to help us shape the experience into how we want it to be,” the company said in a statement.
Rather than developing a full-blown sequel, Microsoft has said its primary concern is keeping the existing Minecraft community happy with updates and new versions of the game, such as the episodic Minecraft: Story Mode and dungeon crawler Minecraft Dungeons, which is set for release in spring 2020.