West Brom close in on Rotherham United's Semi Ajayi
The initial fee is thought to be in the region of £1.5 million with the potential for add-ons to take it to around £2.5m.
Ajayi, who can play as a centre-half or in midfield, was signed by Rotherham boss Paul Warne on a free transfer from Cardiff City in 2017 and has made more than 100 appearances for the club. He has a year left on his contract at AESSEAL New York Stadium.
Warne confirmed on Wednesday that two Championship clubs had submitted offers for the 25-year-old who scored eight goals last season as the Millers slipped into League One.
Rotherham may use the proceeds from any sale to strengthen their interest in Blackpool central defender Curtis Tilt.
West Brom are due at New York on Tuesday for a pre-season friendly.