The Elland Road outfit have agreed a fee with Manchester United for the Wales winger and he was due to travel to Leeds overnight to be in place to complete the move on deadline day.
James is a player that Leeds boss Marcelo Bielsa has wanted since 2019 and the Whites have been forced to dig deep to deliver for the Argentine.
The total fee for James will come to £30m, which will be a club record purchase for Leeds.
The Whites splashed out around £25m to sign Rodrigo from Valencia last summer and James’ arrival will eclipse that sum.
It also represents a substantial profit for Manchester United, who paid an initial £15m to sign James from Swansea City.
The winger faces a season of potentially reduced playing time if he stays at Old Trafford, due to the arrival of Cristiano Ronaldo.
Nevertheless, Red Devils boss Ole Gunnar Solskjaer has been reluctant to sell James.
