Fans and players will be expected to exercise caution despite COVID-19 restrictions being eased when the U.S. Open begins on August 30 with capacity crowds in attendance, the United States Tennis Association (USTA) said.

A year ago the tournament barred fans from attending, while players faced possible fines and expulsion if they exited the tournament's "bubble" without written consent as they were kept largely sequestered from New York City in Long Island accommodations.

This year, they will again be able to dine at Manhattan restaurants and move freely outside their hotel rooms, with Cincinnati Masters winner Alexander Zverev enjoying seats behind home plate at the New York Mets' baseball game against the San Francisco Giants.

Players are required to submit to COVID-19 testing upon arrival in New York but have not been instructed to quarantine while awaiting results.

Tournament director Stacey Allaster said that with almost 70 percent of the New York City population vaccinated, organizers were confident of staging the event safely.

"We heard loud and clear the athletes' mental health through these last 12 months, the isolation in the bubbles, was important, that they could have some flexibility," said Allaster.

The biggest change for players and organizers is the return of fans at Flushing Meadows, which was eerily quiet in 2020.

Their return means millions more in revenue for the USTA, which ran a $180 million budget deficit in 2020 as a result of hosting the tournament without spectators, USTA CEO Mike Dowse said.

"We did make a lot of hard decisions last year," said Dowse. "We had significant salary reductions of our national staff, and we downsized the national organization by over 23 percent. We tapped into our reserves."

New York City professional sports teams began welcoming back spectators months ago, with the New York Knicks and Brooklyn Nets opening their doors to fans in February.

Fans at the Billie Jean King National Tennis Center will not be required to show proof of vaccination or wear masks outdoors.

"We're still relying on the goodwill of people. The unvaccinated, although it's not going to be enforced, they really should be wearing masks," said Brian Hainline.

"It's like any other aspect of New York City; going to the baseball game, you make an informed decision."

The guidance comes as some players, including world No.1 Novak Djokovic and French Open runner-up Stefanos Tsitsipas, have stated they are reluctant to take the vaccine.

But Roger Federer and Rafael Nadal, who are both ruled out of this year's U.S. Open through injuries, have both been vaccinated and have urged their fellow athletes to follow suit.

The USTA said it did not know how many players at the U.S. Open are vaccinated.