The Major League Soccer club confirmed that the central defender, acquired in January from the Chicago Fire, requested a move but will continue to train with the team.
Soumare has played in 10 of Montreal's 16 regular season games, including nine as a starter. But he has been mostly left on the bench in recent games in favour of Wandrille Lefevre and Victor Cabrera. He played the final 25 minutes of the Impact's 3-0 win over Columbus on Saturday after Cabrera developed cramps.
The Malian had his best moments while helping the Impact reach the CONCACAF Champions League final in the spring.
The Impact are also dealing with an issue involving their top central defender Laurent Ciman. The Belgian has asked the club to do more to help his four-year-old daughter Nina's treatment for autism.
A report Wednesday on the website 7sur7 said Ciman's wife, Diana Saiu, told the Belgian newspaper Het Laatste Nieuws it was costing the couple more than $3,000 per week for treatment they thought would be paid by the club.
"They promised the best care but they abandoned Nina," she was quoted as saying. "We are very disappointed."
Ciman asked his club Standard Liege to release him to sign with Impact because he was assured top-level treatment was available for his daughter in Canada.
Impact vice-president Richard Legendre said he met with the Cimans and the team will do all it can to resolve the problem.