WHMCS integration wordpress theme


I posted in TH forum, but i dont think it was the right place, maybe i have better luck here.
We intend to integrate WHMCS into our brand new webhosting theme. I know that exists some WordPress bridge plugin, but does not actually make a bridge between products from WHMCS to WordPress database or WordPress defined products into WHMCS database. Also, users are different (needs to register both on WHMCS and WordPress).
Is there an API to actually bridge WHMCS with WordPress?
Thanks in advance.