(Adds details about state testing capacity, new occupancy rules)
NEW YORK, March 12 (Reuters) - New York State will ban gatherings of more than 500 people beginning on Friday at 5 p.m. (2100 GMT) in order to slow the spread of the new coronavirus, Governor Andrew Cuomo said on Thursday.
Establishments that can fit 500 people or fewer must halve their capacity beginning on Friday, Cuomo said.
Broadway theaters in Manhattan will have to start observing the new rules on Thursday night, Cuomo told reporters at a news conference in Albany. He declined to say how long the ban would last. He said it would be evaluated on a daily basis.
"This is about science, this is about data," Cuomo said in announcing what he described as extraordinary measures for a state that includes the nation's most populous city. "Let the science, let the data make the decisions."
New York City Mayor Bill de Blasio was due to brief reporters later on Thursday.
As of Thursday afternoon, there were 328 people in the state confirmed to have contracted the new coronavirus, which causes a sometimes deadly respiratory disease called COVID-19. A minority of those people have been hospitalized, but so far no deaths have been reported in New York.
Hospitals, nursing homes, mass transit and certain other facilities will be exempt from the new rule, Cuomo said. The rule only applied to "congregant spaces," state officials said: an office building that fits more than 500 people would not be subject to the rule, but a single open-plan office space that fits 500 people would.
In the neighboring state of New Jersey, Governor Phil Murphy recommended the cancellation of all gatherings of more than 250 people.
On Wednesday night, Cuomo announced that the centuries-old St. Patrick's Day parade in New York City, due to take place on March 17, would be postponed to a later date.
Cuomo also expressed frustration with slow progress in ramping up testing capacity, although he declined to attribute blame. The state has authorized 28 labs to carry out diagnostic tests for suspected COVID-19 patients who meet certain criteria, Cuomo said.
"We are way behind in testing," he said. "There'll be plenty of time to do a retrospective. We need to increase testing as quickly as possible and get the volume as high as possible. The more people you test, the more people you can isolate."
The state has also contracted with a national laboratory, which Cuomo did not name, to do automated testing, which speeds up the process, pending approval from the U.S. Food and Drug Administration. Once that is allowed to proceed, the state could run 5,000 tests a day, Cuomo said. (Reporting by Jonathan Allen in New York; Additional reporting by Hilary Russ in New York Editing by Chizu Nomiyama and Howard Goller)