How to assume role and not use access keys?

Terraform Providers
1

I have a very simple need - I want to run terraform from client and keep the state file in S3. Here is what I am trying to do

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = ">= 3.73.0"
    }
  }
  required_version = ">= 0.14.1"
}
provider "aws" {
  region  = "us-east-1"
  assume_role {
    role_arn = "arn:aws:iam::12345678901:role/test-cicd-role"
  }
}


backend.tfvars:

bucket = "cicd-testing-stuff"
key ="cicd-test-aa/terraform.tfstate"

$ terraform init -backend-config="backend.tfvars"

Initializing the backend...
╷
│ Error: error configuring S3 Backend: no valid credential sources for S3 Backend found.
│ 
│ Please see https://www.terraform.io/docs/language/settings/backends/s3.html
│ for more information about providing credentials.
│
│ Error: NoCredentialProviders: no valid providers in chain. Deprecated.
│       For verbose messaging see aws.Config.CredentialsChainVerboseErrors

Just as an FYI, it is in the same account. Is using the access keys the only option ?

2

Adding some more info as I am learning,

Question : Is assume_role only going to work, in case of cross account ?