WASHINGTON — President Trump said on Saturday that he might order a quarantine of New York, New Jersey and parts of Connecticut, a drastic exercise of federal power that would further restrict travel by millions of Americans to prevent them from carrying the coronavirus to other parts of the country.
Mr. Trump offered no details about how his administration would enforce a ban on movements in and out of three northeastern states, including the country’s most populous city, though he said it would not prevent truckers from making deliveries from outside the area and would not affect trade with the three states “in any way.”
Speaking to reporters before traveling to Norfolk, Va., to see off the Navy’s Comfort ship as it deployed to New York to bolster hospital capacity, Mr. Trump said that New York and the other states had become a “hot spot” and that infected New Yorkers had been carrying the pathogen to Florida.
“There is a possibility that sometime today we’ll do a quarantine, short term, two weeks, on New York, probably New Jersey, certain parts of Connecticut,” said Mr. Trump, a former New Yorker who now is officially a Florida resident. “They’re having problems down in Florida. A lot of New Yorkers going down, we don’t want that, heavily infected.”
The president’s musing about a quarantine was the latest example of how he has lurched from one public message to another as his administration struggles to slow the spread of a deadly pandemic, prevent large-scale deaths and minimize the long-term damage to the nation’s economy and way of life.
Just days earlier, Mr. Trump had repeatedly defied the recommendations of his own public health experts by insisting that he wanted to lift social distancing restrictions so that large parts of the country could return to work, perhaps as early as April 12. But on Saturday, the president veered in the other direction, suggesting that even more stringent restrictions, like a quarantine, were necessary to slow the spread of the virus.
“I’d rather not do it, but we may need it,” Mr. Trump said of a quarantine.
The idea comes as the White House’s two-week national coronavirus guidelines — including recommendations to work from home, avoid discretionary travel and limit gatherings to no more than 10 people — are set to expire on Monday. Mr. Trump has not yet said whether he will extend them.
The suggestion from the president that he might prevent residents of the tristate region from leaving their states surprised top officials.
Gov. Andrew M. Cuomo of New York quickly dismissed the idea, calling it “unworkable” and questioned whether the president had the authority to confine vast numbers of Americans in a particular region.
“I don’t even know what that means,” Mr. Cuomo said during an afternoon briefing in Albany. “I don’t know how that could be legally enforceable. From a medical point of view, I don’t know what you would be accomplishing.” Asked about the proposal on CNN, Mr. Cuomo equated it to “a declaration of war on states” and said the plan stood at odds with the law and the president’s desire to restart the economy. “You would paralyze the financial sector,” he said, saying the stock market would “drop like a stone.”
Mr. Cuomo said that he and the president had spoken earlier on Saturday about the arrival of the Navy’s hospital ship, but added, “I didn’t speak to him about any quarantine.” Gov. Philip D. Murphy of New Jersey also said that he was unfamiliar with what Mr. Trump had suggested, and that it had not come up when the two men talked on Friday. Gov. Ned Lamont of Connecticut said in a statement that he looked forward to discussing the proposal with Mr. Trump “because confusion leads to panic.”
White House officials provided no specific information about the legal basis for a mass quarantine of millions of people and Mark Meadows, the president’s incoming chief of staff, said only that the administration was “evaluating all the options right now.” But pressed on the matter, officials referred reporters to a Centers for Disease Control and Prevention website titled “Legal Authorities for Isolation and Quarantine.”
The site asserts that the commerce clause of the Constitution gives the federal government the power to isolate or quarantine people, and that section 361 of the Public Health Service Act authorizes the secretary of health and human services to “take measures to prevent the entry and spread of communicable diseases from foreign countries into the United States and between states.”
Existing regulations indicate that in the event of a federal quarantine, “no such individual shall travel in interstate traffic or from one state or U.S. territory to another without a written travel permit issued by” the director of the C.D.C. or someone acting on his behalf.
But Leila Barraza, an assistant professor of public health at the University of Arizona, said an attempt by the federal government to restrict travel between states was likely to be challenged in court, especially if the president had not tried less draconian measures first.
“There has to be a compelling interest for imposing interstate travel restrictions, and they have to be the least restrictive possible,” she said.
The purpose of a quarantine would be to prevent the spread of a deadly pathogen. But medical experts were split on Saturday about whether such an action would help in the current situation, when the coronavirus has already spread widely around the country. As of Saturday, the United States had more than 119,000 known cases of the virus, with infected patients in all 50 states and Washington, D.C.
Other countries, including India, have embraced severe lockdowns of their citizens, including limits on travel, in an effort to try to prevent the spread of the virus, something that some public health experts said could still be effective in the United States.
But Dr. Amesh Adalja, an assistant professor at Johns Hopkins Bloomberg School of Public Health, countered that Mr. Trump’s musings on a possible quarantine would provide little benefit, given that much of the region is already under fairly strict stay-at-home measures, and might cause people to flee the city, spreading the virus more quickly.
“Just seeing the breaking news alerts on their phones will cause people to leave the city,” Dr. Adalja said. “It could end up creating more flight from New York and more chains of transmission.”
That is just what happened in China after the mayor of Wuhan, where the virus first emerged, began speculating about the possibility of closing his city to keep the virus from spreading to the rest of the country.
Panicked residents of the city — many of whom were already planning to leave for the Lunar New Year holiday — fled. Five million people from Wuhan escaped before air, train, bus and road traffic was finally firmly shut on Jan. 23. Their travel to other parts of the country seeded new outbreaks all over China.
Public health officials around the country have criticized Mr. Trump and his administration for failing to move quickly enough to provide diagnostic testing that could have helped track the spread of the virus earlier. Governors and mayors have pleaded with the president to do more to help them acquire protective gear like masks and ventilators for emergency medical workers, nurses and doctors.
The specter of a federal quarantine came after a wave of governors who, fearful about the virus spreading further through their states, ordered people who had traveled from New York to isolate themselves for two weeks after their arrivals. Gov. Gina Raimondo of Rhode Island said Friday that state troopers would begin stopping drivers with New York license plates so that National Guard officials could collect contact information and inform anyone coming from the state that they were subject to a mandatory, 14-day quarantine.
Mr. Trump floated the idea of a quarantine even as he left the White House for the first time in more than a week to travel to a naval base in Norfolk so he could trumpet the departure of the 894-foot hospital ship, saying that its 1,000 beds would play a “critical role” in freeing up capacity at area hospitals.
In reality, however, the arrival of the Comfort will help the struggling state only on the margins. New York estimates it will need a total of 140,000 beds to treat patients who are ill with the disease caused by the coronavirus, and it has about 53,000 beds during normal times.
“You have the unwavering support of the entire nation, the entire government and the entire American people,” Mr. Trump said.
The president’s decision to turn the trip to the base into a high-profile photo opportunity raised questions about safety and his use of government resources at a time when the administration’s own guidelines advise against most travel and gatherings of more than 10 people.
“We don’t need Donald Trump in Virginia doing a photo op,” Terry McAuliffe, the former Democratic governor of Virginia, said in an interview. “He ought to be staying in Washington, in his job. It’s a total waste of time.”
Mr. Trump delivered his speech in front of a small audience of about a dozen military officials, as well as a handful of White House aides who traveled with him. The ship is expected to take on patients in New York with other illnesses to let hospitals focus on the large number of coronavirus cases, the president said.
A White House official said the trip was proposed partly because the naval station is self-contained and would not require Mr. Trump to be in public areas like a commercial airport.
“It’s like a tiny trip,” Mr. Trump said on Friday, defending his decision to go. “I think it’s a good thing when I go over there and I say thank you. We’ll be careful.”
Charlie Savage contributed reporting from Washington, and Andrew Jacobs, Donald G. McNeil Jr. and Jesse McKinley from New York.