Asynchronous replication between multiple Galera clusters

I have two Galera clusters on different regions and I'd also like to replicate the clusters asynchronously.

Region 1:

Region 1 Node 1
Region 1 Node 2
Region 1 Node 3

Region 2:

Region 2 Node 1
Region 2 Node 2
Region 2 Node 3

Additionally, each node has load balancer

So whenever someone writes on any node of either region, not only Galera replicates the changes synchronously between the other nodes in the same region, the data is also asynchronously replicated on the other region.

Please let me know if this is even possible at all and how I should start.

Thanks!