Asterisk regestration to a 3gpp proxy

I am atempting to get my Asterisk to regester to a 3gpp proxy and it is failing because of the :5060 at the end of the regestration VIA header. The 3gpp spec specifies loose routing which sais the client can not specify the port apon regestration.

Does anyone now if I can stop Asterisk from putting the port on the regestration line. the 3gpp call this loose routing. There is other places in the call flow that the 5060 can not be specified also but I may be able to work around them if I can get past the regestration.

Thanks for any help ( Asterisk newbee )