Durant's business manager, Rich Kleiman, informed Warriors general manager Bob Myers of the decision in recent days.
Durant and Kleiman are together in New York, where they've been mulling Durant's free-agency options. So far, it has been a fairly clandestine process.
Durant is still considering a number of scenarios in free agency, including a return to Golden State, league sources tell ESPN. The New York Knicks, Brooklyn Nets and LA Clippers are also believed to be considerations, sources said.
Durant, 30, can sign a four-year, $164 million deal with another team, and remains eligible to sign a five-year, $221 million deal with the Warriors.
Durant, a two-time NBA Finals MVP with the Warriors, suffered a torn Achilles tendon in Game 5 of the Finals on June 10 and is expected to need the 2019-20 season to fully rehabilitate the injury.
Every team pursuing him is expected to still offer him a full max contract.
Stephen A. sees KD signing with Knicks or Nets
With Kevin Durant declining his player option, Stephen A. Smith believes Durant will end up in New York with the Nets or Knicks.
Sources tell Stephen A. that Dolan is hesitant to offer KD a max deal
Stephen A. Smith reports that Knicks owner James Dolan wants to see Kevin Durant's medical records before offering him a max contract.