Manchester United midfielder Henrikh Mkhitaryan has agreed to join Arsenal, with Alexis Sanchez set to move in the opposite direction in a straight swap.
Armenia international Mkhitaryan, 28, will have a medical over Sunday and Monday, while Chile forward Sanchez, 29, will have his on Sunday.
The length of Mkhitaryan's contract, and his salary, is undisclosed.
Gunners boss Arsene Wenger had earlier said Sanchez would only join United if Mkhitaryan moved to Arsenal.
Sanchez missed Arsenal's 4-1 win over Crystal Palace on Saturday.
"He didn't play because you cannot drive up north and play football at the same time," said Wenger.
United boss Jose Mourinho, meanwhile, said a deal to sign Sanchez was "so close" following his side's 1-0 win at Burnley on Saturday.
An announcement is now expected in the next 48 hours.
The Red Devils beat Arsenal to Mkhitaryan's signature when he signed for the Old Trafford club for £26.3m from Borussia Dortmund in July 2016.
He has made 63 appearances for United - 22 this season - scoring 13 goals.
Sanchez, meanwhile, has scored 80 goals in 166 appearances in all competitions for Arsenal since joining them from Barcelona for £35m in July 2014.
The Chile international, whose contract Arsenal was due to expire in the summer, had looked set to join Manchester City last August. However that move fell through on transfer deadline day after Arsenal failed to sign a replacement.
It emerged this week that City had decided not to pursue their interest in signing Sanchez during the current transfer window.
Arsenal are now in talks with Dortmund about the potential signing of striker Pierre-Emerick Aubameyang. They will need to pay in excess of £50m for the Gabon international, say sources close to the German club.
Analysis - 'Good business for both clubs'
Former England and Newcastle striker Alan Shearer on Match of the Day
I think it is good business for both clubs.
Arsenal are getting rid of a player who doesn't want to be there, but they are also getting a player whose face maybe didn't fit at United, but who is much better than he's shown at United.