jitsi --> kamailio <-----> pstn.gw

jitsi is registered using TCP

SIP Trunk between kamailio and pstn.gw is using TCP

Initial invite from jitsi to kamailio is sent using TCP but invite sent  from kamailio to pstn.gw is being sent with UDP.

How can I configure kamailio to send invite to pstn.gw with TCP?

Thank You