The Blades striker - who has bagged 15 goals this season - is struggling with a hamstring injury.
His last appearance came in the 3-1 win at Reading last month, missing the last three games.
"Leon is close," said Blades manager Chris Wilder. "We're hoping.
"We'd love to have him involved in the squad.
"We want everybody to be fit. He'll definitely be okay after the international break.
"We'll sit down and have a chat. Leon knows his body better than anybody so of course he'll be involved in that."
United are two points off the play-offs, with nine games remaining.