The 23-year-old midfielder has been linked with a move to Villa Park in recent weeks following a stunning season under Marcelo Bielsa at Elland Road.
Leeds have now moved to tie down Phillips long-term, whose current deal has two years left to run until the summer of 2021.
He was a key figure under the Argentine in West Yorkshire last season making 44 Championship appearances for the Whites.
Phillips was the linchpin in Bielsa’s midfield in a deep-lying role and was also used in the centre of defence as cover on occasion. He bagged one goal and three assists despite his new-found defensive position.
Reports emerged last month that Villa had made the midfielder one of their top targets in the transfer window following the club’s promotion to the top-flight.
Dean Smith guided his side to Championship play-off glory at Wembley in May as they defeated Derby County 2-1.
Leeds, though, appear keen to rebuff the advances of Villa as they attempt to keep hold of the Thorp Arch academy product.
United this week began to shape Bielsa’s squad for the upcoming campaign with the additions of Helder Costa, Jack Harrison and Ben White.
Youngster Jack Clarke briefly departed the club to join Tottenham Hotspur in a deal worth an initial £9million before the 18-year-old immediately returned on a season-long loan.