“We’re not going to be able to provide basic services and actually have a normal society if we don’t get help from the federal government,” Mr. de Blasio said in an interview with CNN.

“Our revenue is gone, our tax base is gone, our economy is gone,” he said. “Five to 10 billion is the amount of money we’ve lost that we would normally use to be able to support our first responders, our basic services, everything that keeps the biggest city in America going.”

The Independent Budget Office, a nonpartisan city agency, forecast on Wednesday that the city would shed roughly 475,000 jobs in the 12 months that started April 1, resulting in an estimated tax revenue shortfall of $9.7 billion in fiscal years 2020 and 2021.

Mr. de Blasio said that the budget office’s forecast was “pointing in the right direction,” but he added, “We’re going to lose much more after that. Remember, the revenue losses are deepening.”