Kompany has not played since January due to a calf problem but has reported for duty ahead of the World Cup qualifying double-header against Macedonia.
Belgium assistant head coach Vital Borkelmans insists no decision has yet been made on whether the 26-year-old defender will play but has stressed his importance to the country.
"Vincent is now training with the physical coach," Borkelmans told Sky Sports News. "He also trained very hard at City.
"He is very important for the group and we are quite happy he is here. We will make a decision on Wednesday or Thursday whether he can play or not."
The news is likely to upset Manchester City manager Roberto Mancini, who appeared to anticipate Kompany sitting out the international fixtures in order to recover fully.
"We don't want to take a risk at this moment because we have one game and then it is the international break so it's best he is recovering," said Mancini before facing Everton last week.
"The calf is a dangerous injury. If you don't recover very well then you can have a problem for four, five or six weeks in a row."
But when pressed on whether there is a dispute with City, Borkelmans added: "We talk many times with the coach [at City] but Vincent is very important to us. He is the captain of the team."