WASHINGTON (Reuters) - U.S. President Donald Trump moved on Wednesday to accelerate production of desperately needed medical equipment to battle the coronavirus pandemic and said an estimate that U.S. unemployment could conceivably reach 20 percent was a worst case scenario.

Scrambling to address the virus after initially playing it down, Trump said he is invoking the Defense Production Act, putting in place a law that will allow the U.S. government to speed production of masks, respirators, ventilators and other needed equipment.

“We’re going to defeat the invisible enemy,” said Trump, who said the unfolding crisis had basically made him a “war-time president.”

Trump said he would invoke another law that would allow U.S. authorities to turn back migrants seeking to cross the southern border of the United States illegally. The border will not be closed, he said.

“No, we’re not going to close it, but we are invoking a certain provision that will allow us great latitude as to what we do,” he said.

Trump has made staunching the flow of migrants across the border with Mexico a central pillar of his presidency and has poured billions of dollars into building a border wall that is far from completed.

Immigrant rights groups have slammed the idea of mass returns of foreign nationals to Mexico.

U.S. President Donald Trump addresses the daily White House coronavirus response briefing with members of the administation's coronavirus task force at the White House in Washington, U.S., March 18, 2020. REUTERS/Jonathan Ernst

Trump said a hospital ship will be sent to hard-hit New York to help people affected by the contagion, and that a second hospital ship will be deployed on the West Coast.

He defended his description of the coronavirus as “the Chinese virus” despite concerns among some Americans that he was making an ethnic slur.

“It’s not racist, not at all. It comes from China,” he said of the illness, whose origin has been traced back to Wuhan, China.

Trump, appearing in the White House briefing room for what has now become a daily news conference with his coronavirus task force, said he would sign the Defense Production Act later on Wednesday.

The law, which dates back to the Korean War of the 1950s, grants the president broad authority to “expedite and expand the supply of resources from the U.S. industrial base to support military, energy, space, and homeland security programs,” according to a summary on the Federal Emergency Management Agency website.

Reuters was first to report last month that Trump's action was being considered. (reut.rs/2U0TVqk)

“We will be invoking the Defense Production Act just in case we need it,” said Trump.

Treasury Secretary Steven Mnuchin fanned fears of economic collapse on Wednesday by telling lawmakers on Capitol Hill that 20 percent unemployment was an extreme possibility should the virus have devastating effects on American businesses, many of which are already under duress.

“That’s an absolute total worst case scenario,” said Trump. “We’re nowhere near it.”

Vice President Mike Pence, head of the coronavirus task force, urged all Americans to put off elective surgery to allow hospitals to concentrate on the rising influx of patients with the COVID-19 respiratory illness caused by the new virus.

Deborah Birx, a member of the task force, urged young people to adhere to government guidelines, calling for a 15-day effort to slow the spread of the virus. Young people are considered key transmitters of the virus, which can be passed along even with mild or no symptoms.

There are now more than 7,300 U.S. cases of the illness and at least 118 deaths.