Defoe is a target for QPR, after missing out on the move on deadline day last month.
Leiweke, president and chief executive of Maple Leaf Sports and Entertainment, Toronto's parent company, said at the Leaders in Sport conference in London: "Jermain Defoe is focused on the remaining four games (of the regular season).
"Jermain understands the uniqueness of Major League Soccer, we have play-offs. That's the defining moment on the success of our clubs.
"Making the play-offs would be a huge step forward (for Toronto). Jermain now gets that and is totally focused on that.
"As to what happens during the next transfer window, we've all agreed we'll put it on hold and talk about that in December.
"I compliment Jermain for being committed to trying to get us to the play-offs and making that the only concern that we have right now."
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