Lewis posted a sixth-round TKO of Klitschko on June 21.
The WBC heavyweight champion took the fight on two weeks' notice and was not very impressive.
Lewis was trailing, four rounds to two on all three judges' scorecards, when the fight was stopped because of a huge gash across Klitschko's left eyelid. The cut needed more than 50 stitches to close.
Lewis said negotiations for a rematch are in the early stages.
"We're speaking to Vitali's people as we speak. We want an independent doctor to check it out to make sure he will be available," Lewis said about Klitschko's eye.
Lewis, who is under contract with HBO, said the fight most likely will be in November or December. Originally, he was slated to fight Kirk Johnson on June 21, but Johnson pulled out of the fight because of an injury.