Novak Djokovic has formally withdrawn from the draw for the Indian Wells tournament, organisers said on Sunday in an indication that the world number one's application for a COVID-19 vaccine waiver to enter the U.S. might have failed.

The Serbian, who is one of the most high-profile athletes unvaccinated against the virus, applied to the U.S. government last month for special permission to play at ATP Masters events at Indian Wells and Miami.

"World No. 1 Novak Djokovic has withdrawn from the 2023 BNP Paribas Open. With his withdrawal, Nikoloz Basilashvili moves into the field," organisers said in a statement late on Sunday.

The U.S. currently bars unvaccinated foreigners from entry into the country, a policy that is expected to be lifted when the government ends its COVID-19 emergency declarations on May 11.

Djokovic has not competed at the back-to-back ATP Masters events in Indian Wells and Miami, two of the biggest tournaments on the ATP calendar and known as the "Sunshine Double", since 2019.

No one from Djokovic's team was immediately available to comment on the withdrawal.

Last Friday, Florida Senators Rick Scott and Marco Rubio wrote a letter to U.S. President Joe Biden urging him to grant the waiver request.

Indian Wells tournament director Tommy Haas, the United States Tennis Association and the U.S. Open were among those also hoping the 22-time Grand Slam champion would be allowed to enter.

He would have been a heavy favorite to win his sixth Indian Wells title when the tournament kicks off in the Southern California desert on Wednesday.

Djokovic, who missed last year's Australian Open due to his vaccination status and was not allowed into the U.S. for last year's U.S. Open, has said he would skip Grand Slams rather than have a COVID shot.

He won his record-tying 22th major championships at the Australian Open in January.