Bentley is to undergo a medical during the weekend before completing a temporary move to St Andrew's. The former Blackburn player has slipped down the pecking order at White Hart Lane and is desperate to resurrect his career.
Bentley began his career with Arsenal and then moved to Blackburn after an initial loan spell.
Spurs splashed out £15million to sign Bentley in the summer 0f 2008 but he has found his first-team opportunities with the North London club increasingly limited.
The Peterborough-born player, 26, has so far won seven senior England caps and would be a ready-made replacement if Sebastian Larsson, who is out of contract in the summer, decides to leave Blues.
Newcastle are interested in signing the Sweden international.