Call an authenticated service using service account

I have my flutter app running under a service account and my API running under another service account. My API only accepts authenticated access. I am using the architecture described [here](https://cloud.google.com/run/docs/tutorials/secure-services).

I tested access to it using CURL and using "gcloud auth print-identity-token flutter-identity-sa" command to generate the identity token and it works fine.

Then I tried to implement the code on Flutter using the clientViaServiceAccount method and passing ServiceAccountCredentials but I got a 403 error. I checked the call in the browser and the request is being made using the access token instead of the identity token in the authorization header. Is there a way AuthClient uses the identity token in the authorization header?

Thank you!