The Dutch defender has been at the Vitality Stadium for three years on a permanent basis, having spent the 2016-17 season on loan at the club. He became their record transfer with a fee in the region of £20m.
He had been linked with a return to Chelsea, but City appear to have stolen a march on their rivals and will now be confident of landing the 25-year-old.
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Pep Guardiola's side struggled at the back last term as they were well beaten by Liverpool in the Premier League title race, losing a total of nine games, just one fewer than they had in the previous three seasons.
Aymeric Laporte was a long-term absentee at the back, while Nicolas Otamendi and John Stones also struggled with injuries and form, leaving Guardiola to field midfielders Rodri and Fernandinho as makeshift centre-backs frequently.
They have high hopes for Spanish youngster Eric Garcia but Guardiola has moved to land another front line defender as they look to wrestle the title from Jurgen Klopp's side.