asterisk users - Jun 2004 - SIP clients, H323 client as gateway?

I have several SIP clients which connect to Asterisk. 

Is it possible to use a H323 client account (username/password
combination) as a gateway/proxy for these SIP clients when they need
to call someone on this H323 network, just like using an IAX2-gateway
(registering an username/password combi).

I took a look in the archives, but couldn't find anything related. But
then again, I might not have looked carefully enough ;)

Thanks,

Ralf