The French centre-back is widely thought of as one of the very best young players in Europe, and has been attracting attention from top sides across the continent for some time.
City came close to agreeing a deal for the 23-year-old last month, but baulked at Porto’s valuation of their man on deadline day.
Since then United have become the favourites to land Mangala, with David Moyes’ men having already upped their scouting of the tough-tackling enforcer.
But Pellegrini is ready to revive his interest as he looks to further extend the current gulf between the two Manchester sides.
The Chilean recently irked United by claiming that the Etihad Stadium outfit are the city’s bigger team, which started a war of words between former players and pundits.
Reports suggest that the Capital One Cup finalists are willing to go north of £30m for Mangala in the next window, and they may even increase their offer if Moyes decides to go toe-to-toe with them.
The player’s decision might ultimately lie with the team who offer the best chance of silverware, which may be City if United miss out on Champions League qualification.