I have an web application which is deployed in two aws regions. Each application is linked to its own cognito user pool.
Application A <-> User Pool A
Application B <-> User Pool B
This application has a React frontend that uses aws-amplify ( without hosted UI ) to take care of the authentication and all that.

Now, my dilemma is, how would I be able to achieve the following scenario?
User from pool A can authenticate in Application B
User from pool B can authenticate in Application A
This to be done seamlessly, using a single set of credentials.

Would a single cognito user pool be a better approach for this scenario ?