Palace have lined up a move for Blackman during this month's transfer window as they look to bolster their attacking options.
Eagles boss Ian Holloway has money to strengthen his squad from the sale of Wilfried Zaha and he has made Blackman one of his top priorities.
Blackman has impressed for Sheffield United this season since his arrival from Blackburn last summer.
The 23-year-old has scored 14 goals this season and Palace are keen to bring him in to bolster their promotion bid from the Championship.
News of Palace's interest in thought to have alerted a number of other clubs to Blackman's possible availability this month, but the Eagles are hoping to win the race for the forward's signature.