Alderson said agent Peter Greenberg rebuffed the team's efforts to talk about an extension for the 28-year-old free agent-to-be, who is having his best season with the Mets.
"He wants to focus on baseball," Alderson told MLB.com. "He wants to focus on what's going on on the field. So with that in mind, we will respect his wishes and hopefully pick up negotiations at the end of the season."
Reyes is batting .341, tops in the National League, with a major league-best 12 triples and 26 stolen bases, second-most in baseball.
His decision forces the financially-strapped Mets ownership to make a decision on whether to trade him before the season ends or risk having him walk away for little in return if they can't meet his demands after the season.