A method and a system for supporting rendezvous based instant group conferencing among mobile users allows a conference originator to initiate and setup instant group conferencing to a set of participants even when the participants may not be immediately available to commit to the conference call at the time of its initiation. All negotiations for obtaining commitments from the participants are performed by the system, thus relieving the originator of the time consuming task of negotiating with the participants. The system automatically decides as to when to actually dial out to the participants to setup the conference call after obtaining commitment from all (or a quorum of) required participants.