The U.S. currently bars unvaccinated foreigners from entering the country, though the policy is expected to be lifted when the government ends its COVID emergency declarations in May.

Djokovic unsuccessfully applied to the U.S. government for special permission to play at Indian Wells and Miami.

Carlos Alcaraz leapfrogged the Serb back into top spot in the world rankings after winning the Indian Wells title on Sunday.

"I have no regrets," Djokovic told CNN. "I've learned through life that regrets only hold you back and basically make you live in the past.

"I don't want to do that. I also don't want to live too much in the future. I want to be as much as in the present moment but of course think about future, create a better future.

"So I congratulate Alcaraz. He absolutely deserves to come back to number one."

Djokovic said it was a pity he was not allowed to compete in the U.S. where he has enjoyed plenty of success including three of his 22 major titles.

"But at the same time, it's the conscious decision I made and I knew that there is always a possibility that I won't go," Djokovic said.

"It's the current state or current situation that I hope will change for later this year, for the U.S. Open. That's the most important tournament for me on American soil."

The Serb said the controversy had not dented his enthusiasm for the sport.

"Actually, the contrary, I'm as enthusiastic as ever, as motivated as ever for the sport, my family, my foundation, all the projects and everything I'm doing off the court," he said.

"The dignity, and integrity, and staying true to myself, and my beliefs and my rights are above everything."