I am adding leads to a specific account for distribution to the sales staff through the Soap Web Services API.  I would like to have the lead assigned to the correct sales individuals based upon the assignment rules we will create.  How do I trigger the assignment rule through the Soap Web Services API?

I am adding leads to a specific account for distribution to the sales staff through the Soap Web Services API.  I would like to have the lead assigned to the correct sales individuals based upon the assignment rules we will create.  How do I trigger the assignment rule through the Soap Web Services API?