Novak Djokovic has withdrawn from BNP Paribas Open in Indian Wells and the Miami Open as coronavirus rules prevent him from entering the United States.
The Serbian has pulled out of the two prestigious events after the CDC (Centers for Disease Control and Prevention) confirmed that he needed to be vaccinated to enter the country.
The 20-time major winner revealed last month that he had not received any coronavirus vaccination, insisting he would forego big tournaments "because the principles of decision-making on my body are more important than any title or anything else".
He remains true to his word, missing out on two of the biggest tournaments in the ATP Tour calendar.
The world number two said on social media: "While I was automatically listed in the @bnpparibasopen and @miamiopen draw, I knew, given the entry requirements to the US, it would be unlikely I'd be able to travel there.
"But as international COVID regulations are always being amended, I wanted to wait and see if anything would change.
"The CDC confirmed today that regulations are not changing which means I will not be playing in the US.
"I know my fans are looking forward to seeing me play again and I hope to be back playing for them on the tour soon. Good luck to everyone who is playing in the US in these great tournaments."
The decorated Serbian, who played his first tournament of the year in Dubai a fortnight ago and was overtaken as world number one by Daniil Medvedev last week, is the only man in the top 100 who remains unvaccinated.
He was deported from Australia in January after the government cancelled his visa over his vaccine status.
Djokovic's lack of vaccination became a major flashpoint stretching far beyond the tennis world, with the player detained in quarantine hotels amid extended political wrangling.
A statement on the Indian Wells tournament's Twitter page said: "Novak Djokovic has withdrawn from the BNP Paribas Open. As the next player in line to be seeded, Grigor Dimitrov will move into Djokovic's space in the draw, and a Lucky Loser from qualifying will move into Dimitrov's space in the draw once qualifying is complete."
The 34-year-old is likely to remain in Europe and prepare for the clay-court swing, which gets under way next month.