Ask HN: Any APIs for domain name booking?

I have a cloudfuji like business where I let people create custom instances of a particular software.

Currently I give them *.myhost.com subdomain names but then I see a business opportunity in giving tlds. I want this process to be fully automatic since I am the only one working on this project.

Is there any ISP who sells domain names through APIs ?

I'd presume that any sane registrar will have it, I know my favorite registrar (Gandi) has an API for resellers. I have never used it to testify on its quality though.