The mayor says the City has only met 3 of the seven health indicators that the state requires to begin reopening.
Those indicators include new hospitalizations, hospital bed vacancy rate, intensive care bed vacancy rate and at least 30 working contact tracers per 100,000 residents.
"If the question is do we believe we'll meet all seven state indicators, yes. When? The first half of June," de Blasio said. "You can't guarantee anything in life."
Phase one of reopening in New York allows regions to resume manufacturing and construction. Retailers can reopen with restrictions.
Even when the City begins to reopen, the process will be a slow one.
"Our goal is to get it right the first time," he said. "we're not opening up the floodgates all at one. We've seen other places do that, and they paid dearly for it."
City employees who are now working remotely will continue to stay home for the "foreseeable future," the mayor said.
De Blasio added that the City is considering all options including alternating days for students and remote learning.
MORE CORONAVIRUS COVID-19 COVERAGE
COVID-19 Help, Information and Resources
New York state
Grieving the lost: Tri-State residents who have died
Share your coronavirus story with Eyewitness News
Stimulus check scams and other coronavirus hoaxes
Coronavirus prevention: how clean are your hands?
Centers for Disease Control and Prevention on coronavirus
Total count of NYC COVID-19 cases based on patient address