Michael Beale wants Whittaker adding to his squad at Ibrox, but Rangers have had difficulty agreeing a fee with Swansea.
Whittaker is keen to move on from Swansea, but the clock is ticking down on the transfer window and he is still in Wales.
And Swansea are working hard to make sure that if they do sell Whittaker they are getting the very best deal possible.
The winger spent the first half of the season on loan in League One at Plymouth Argyle, where he made 31 appearances, scoring nine goals and providing seven assists.
Rangers have so far only made one bid for Whittaker, which Swansea turned down.
Swansea are already losing one attacker before the window closes with Michael Obafemi heading to link up with Championship leaders Burnley.
The Welsh giants will be keen to make sure they are not left shorthanded in attack if they do sanction an exit for Whittaker.