Palace are also close to the loan signing of Aston Villa forward Evann Guessand.
The Eagles, who looked at signing the 24-year-old last summer, are set to take Guessand until the end of the season in a deal that will give them an option to buy.
Guessand has scored twice in 26 Villa appearances – both in the Europa League – having struggled to establish himself in his favoured central striker position.
The £18.25m arrival of Tammy Abraham from Besiktas this week also leaves him as likely third choice behind Abraham and Ollie Watkins.
And although the Ivory Coast international has been happy to fight for his place at Villa Park, he is expected to leave.
Guessand has made just six Premier League starts since joining Villa from Nice for £26m last August.
