Initiate Invoice Approval workflow through Rest API

We create AP Invoices (in Oracle fusion cloud) from a third-party application using Rest API. We are able to validate the Invoice after the creation using the Rest API call. However, we do not see a provision to trigger approval workflow for the Invoice through a Rest API call.

The two options I see are as follows.

i. Manually initiate the approval workflow by accessing the Invoice online.

ii. schedule the ESS job to trigger approval workflow for eligible invoices.

We currently use the scheduled batch process that runs every 4hours, but this is delaying the Invoice approval. For other reasons, we will not be able to increase the schedule frequency.