[SR-Users] How to proxy/authenticate on third party sip server?

[intel at intrans.baku.az]

Can anybody help me with configuration kamailio to authenticate call on
3rd party server?

I want to authenticate(and proxy) call's on other server.

for example, user A have account on my server(let it be A at myserver.com)
and account on other server (let it be AA at hisserver.com)
myserver.com keeps A's credentials for AA at hisserver.com
when A is registered on myserver.com, he make call to B at othersip.com
(using myserver.com as a proxy)
Kamailio on myserver authenticate itself on hisserver as AA at hisserver.com,
makes call to destination, and connect it to A.

How can I setup kamailio for such behavior?
Which module should I use?
UAC seems can authenticate on another server, but I don't sure that it do
what I want. (I've tried it, but without much success)