Specifically, Mr. Cuomo said that bar patrons in Manhattan and the Hamptons on Long Island had been flouting the rules, and warned that if local officials did not crack down on such behavior the state could be forced to suspend re-opening plans.

“There is a very real possibility that we would roll back the reopening in those areas,” he said, adding that if people didn’t abide social distancing rules, including wearing masks, a second wave of infections was almost inevitable. “It will come. And once it comes, it’s too late.”