Create Invoice and Invoice Items from Sales Order via API

Create Invoice and Invoice Items from Sales Order via API

Currently, when creating an Invoice associated with a Sales Order via the API, it appears that I must manually include all of the items (line_items) even though they are already part of the Sales Order. My question is this: is it possible to raise an Invoice via the API based on all of the information associated with a Sales Order--such as the  items? In other words, do I always have to manually include the items (line_items) when raising an Invoice via the API when the Invoice is associated with an existing Sales Order (salesorder_id)?

Thank you!

Chris