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President Trump said Tuesday the federal government plans to send 400 ventilators to New York City, with more equipment on the way.

“The World market for face masks and ventilators is Crazy. We are helping the states to get equipment, but it is not easy. Just got 400 Ventilators for @NYCMayor Bill de Blasio,” Trump tweeted Tuesday morning. “Work beginning on 4 hospitals in New York! Millions of different type items coming!”

The shipment represents a fraction of the 15,000 ventilators Mayor Bill de Blasio called for last week as the city and state become the epicenter of coronavirus in the United States. De Blasio repeatedly has sounded the alarm on the shortage of ventilators in New York City hospitals, as many COVID-19 patients need the machines to help them breathe.

CORONAVIRUS VENTILATOR DEMAND

De Blasio has also sought millions of N-95 masks and more Personal Protective Equipment (PPE) for medical professionals.

"If we don’t get ventilators this week, we are going to lose lives we could have saved — I can’t be blunter than that,” de Blasio said on CNN Monday.

New York now has more than 23,000 positive cases of coronavirus in the state, with roughly half of that in New York City.

De Blasio, over the weekend, said he had asked for Trump to use the Defense Production Act to acquire ventilators for patients suffering from the illness.

On Tuesday, the president said the act was "in full force," but that he did not need to use it: "The Defense Production Act is in full force, but haven’t had to use it because no one has said NO! Millions of masks coming as back up to States."

The Defense Production Act, which was first enacted in 1950 as a response to the Korean War and has since been re-invoked more than 50 times, is meant to streamline the production of medical supplies to help the country battle the coronavirus pandemic and require businesses to sign contracts or fulfill orders deemed necessary for national defense.

Under the act, companies are required to accept and prioritize contracts from the government and to prioritize “materials, services and facilities to promote the national defense or to maximize domestic energy supplies.” While this provision has historically been used to ramp up military production, amid the COVID-19 pandemic the act will be used for medical supplies.

Meanwhile, Trump also referred to the temporary hospitals in New York City. New York Gov. Andrew Cuomo announced over the weekend four sites in the state that will serve as additional space for hospitals overflowing due to the coronavirus outbreak.

CUOMO SAYS TEMPORARY HOSPITALS IN NEW YORK TO INCLUDE JAVITS CENTER

The four initial sites recommended by the Army Corps of Engineers are the Jacob K. Javits Convention Center in New York City, locations at SUNY Stony Brook in Long Island, SUNY Old Westbury and the Westchester Convention Center.

"We have a plan of action to help stop the spread of this virus, including expanding hospital capacity and identifying new hospital beds, and after meeting with the Army Corps of Engineers and hearing their recommendations, we stand ready for the building of temporary hospitals at four facilities in New York State,” Cuomo said Saturday.

The sites were identified by an inspection team led by the Army Corps of Engineers and included state officials from New York’s Office of General Services, the Dormitory Authority of the State of New York, the New York Department of Health and the New York State Division of Military and Naval Affairs. The team visited more than a dozen sites to review their capability to serve as temporary hospitals, Cuomo’s office said.

The World Health Organization declared COVID-19 a pandemic earlier this month.

As of Tuesday morning, the U.S. had more than 46,000 positive cases across the country. Nearly 600 people have died.

Fox News' Ronn Blitzer and Andrew O'Reilly contributed to this report.