Kyle Walker will undergo his Manchester City medical on Friday as Pep Guardiola's side close in on the signing of Tottenham's England international.
Press Association Sport understands City will pay £45million up front for the 27-year-old right-back, with further adds on that could take the eventual price up to a maximum of £50million.
Walker will therefore not become the outright most expensive defender ever, an honour that currently belongs to David Luiz following his £50million transfer from Chelsea to Paris St Germain in 2014.
The £47.5million City spent on centre-back John Stones last summer would also be greater than the initial fee they are giving Spurs.
Guardiola has been keen to upgrade the full-back regions after Pablo Zabaleta, Bacary Sagna and Gael Clichy all left the Etihad Stadium at the end of last season.
The pacy Walker made over 180 Premier League appearances for Spurs since joining from Sheffield United in 2009 and has 27 international caps.
His move to City should be completed by the time they head on their pre-season tour to the United States next week, and Walker may come up against his old team-mates given there is a friendly fixture with Spurs in Nashville on the calendar.
Walker would be the third signing of the summer so far for City, who have already brought in midfielder Bernardo Silva from Monaco and goalkeeper Ederson from Benfica from a combined £77.5million.
Spurs themselves returned to pre-season training on Friday and Walker's spot in the team looks set to be filled by his England team-mate Kieran Trippier.