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The city has taken the biggest hit in the country from the coronavirus pandemic. De Blasio stressed the need to stay closed even as many states begin to lift restrictions and reopen businesses.
"For folks in local communities who walk on the beach, walk on the boardwalk, they can still do that. But no swimming, no lifeguards, no congregating," de Blasio told "Sunday Morning Futures."
"I don't want to do it, but if I have to, I will," he said of the possible fencing.
De Blasio added that the New York Police Department and Parks Department will be deployed to ensure that the rules are carried out.
"Our beaches get very crowded very quickly," de Blasio told Maria Bartiromo. "We are so far from being out of the woods here in the epicenter, and until we are safe, no beaches are open."
The prolonged shutdown has hammered the city's tax income, and the mayor said the city will continue to see revenue losses.
While New York says it needs $7 billion in federal stimulus aid because of the coronavirus pandemic, President Trump says he's not about to bail out states that are trying to use this crisis to make up for years of mismanagement.