World number one Novak Djokovic will not play at this year's Miami Open after a bid to apply for special permission to enter the United States failed.
Proof of vaccination will be required to enter the United States until April 10, and Djokovic - who is unvaccinated - had to apply for a special exemption to compete in March's tournaments.
The 22-time Grand Slam winner was also forced to miss the ongoing Indian Wells Masters for the same reason, and Miami Open director James Blake has now conceded defeat in his efforts to allow Djokovic to play.
"We did all that we could. We tried to talk to the government, but that's out of our hands. We tried, and he wasn't able to play," Blake told the Tennis Channel, as quoted by BBC Sport.
"Same result that he had in Indian Wells, where I know [fellow tournament director] Tommy Haas did as much as he could. We tried to get Novak Djokovic to be allowed to get an exemption, but that wasn't able to happen."
Djokovic has won six titles at the Miami Open, prevailing at the 2007, 2011, 2012, 2014, 2015 and 2016 editions, but he has now been forced to miss the last three tournaments.
The 35-year-old won the Australian Open and Adelaide International 1 in January, but he lost to Daniil Medvedev in the semi-finals of the Dubai Tennis Championships last month.