Top US health and infectious disease specialist Anthony Fauci has raised the prospect of US professional sports leagues cancelling their seasons if the safety of players and fans cannot be guaranteed.

In an interview with the New York Times, Fauci said the key to ending the coronavirus sports lockdown would be widespread testing across North America that delivers speedy results.

Sport in North America ground to a standstill in March as the Covid-19 pandemic swept across the continent, with every major professional league either suspending or delaying their respective seasons.

Several leagues are now studying ways that could allow for a return to competition, with basketball and baseball mulling plans which include sequestering teams in locked down locations and playing games in empty arenas.

Fauci however believes that leagues may need to confront the option of cancelling a season if safety cannot be guaranteed.

"Safety, for the players and for the fans, trumps everything," Fauci told the Times.

"If you can't guarantee safety, then unfortunately you're going to have to bite the bullet and say, 'We may have to go without this sport for this season.'"

While President Donald Trump has spoken enthusiastically of sports returning "sooner rather than later", state officials have been more circumspect.

On Tuesday, California Governor Gavin Newsom said live sports with fans in attendance would only take place once stay-at-home orders had been lifted.

In his interview with the Times, Fauci, the director of the National Institute of Allergy and Infectious Diseases, said there was a risk of a Covid-19 resurgence if restrictions were lifted too soon.

"If we let our desire to prematurely get back to normal, we can only get ourselves right back in the same hole we were in a few weeks ago," Fauci said.

"I would love to be able to have all sports back," he added. "But as a health official and a physician and a scientist, I have to say, right now, when you look at the country, we're not ready for that yet."

Fauci said plans floated by the NBA and Major League Baseball to resume play without spectators were possible but would likely be "logistically difficult."

"I'm not saying this is the way to go, but you want to at least consider having players, if they're going to play, play in front of a TV camera without people in the audience," Fauci said. 

"And then test all the players and make sure they're negative and keep them in a place where they don't have contact with anybody on the outside who you don't know whether they're positive or negative.

"That's going to be logistically difficult, but there's at least the possibility of doing that."