It is understood that Spurs have offered an initial £28million with a potential £14m to follow in add-ons for the talented defender.
Sanchez looks set to pen a five-year deal at White Hart Lane and become Mauricio Pochettino's first signing of the summer.
The Colombian is likely to replace Kevin Wimmer, who is on the verge of joining West Brom.
The Baggies have been searching for defensive reinforcements all summer and with Manchester City stepping up their interest in captain Jonny Evans, Tony Pulis will be keen to get a deal over the line for the Austrian.