use administrator access on support connections with link

If  a users machine has UAC enabled and they are not an administrator and the control client hasn't been installed, whenever me as the technician requests access the support session is halted until and administrator enters the credential. in most case this may be one of our clients that we have administrator access for however we cant continue with the session and i cant give a regular user  power user credentials or that of the administrator, how do we get around this ?