(Bloomberg) — President Donald Trump warned that deaths from the coronavirus in the U.S. will escalate over the next one to two weeks, and could be on par with the number of fatalities seen in world wars.

“There’s going to be a very, very deadly period, unfortunately,” Trump told reporters at the White House on Saturday.

The president said that as the number of deaths peak, “I really believe we probably have never seen anything like these kind of numbers, maybe during the war — a world war. A World War I or II or something.”

Trump didn’t give any estimates of how many will die in the coming weeks. Earlier this week, Trump administration officials said as many as 200,000 Americans could die from the virus, less than if the government hadn’t taken aggressive mitigation steps.

Governors and state health officials have raised alarm about a lack of ventilators in some areas, saying shortages will likely lead to deaths among victims who are critically ill. The soaring rate of infections is straining hospitals — especially in New York — that are struggling to care for infected patients and obtain desperately needed supplies.

Trump told reporters his administration is working to lose as few lives as possible and is distributing ventilators to states that need them the most.

Cities in Trouble

More than 300,000 people in the U.S. have contracted the virus and more than 8,000 have died, according to Johns Hopkins University.

Administration officials raised concern about increasing deaths in cities, including New York, Detroit and Chicago. They said they’re also closely watching an upswing in cases in New Jersey, Pennsylvania, Colorado, Connecticut, Rhode Island and the District of Columbia.

“This is the moment to do everything you can” by following guidelines on social distancing and avoiding crowds, said White House virus task-force coordinator Deborah Birx.

She said guidelines encouraging social distancing are working, and that new cases in some areas will start going down. An increase in deaths in the next week will be a result of people who were infected several weeks ago, she said.

“As much as much as you go up, you have to come down the other side because coming down is a reflection of the cases that were coming in before,” Birx said.

Vice President Mike Pence told Americans not to be discouraged by deaths in the weeks ahead.

“It’s going to be a difficult week for the American people,” Pence said.

Projections made public last weekend about the number of people who may die from the virus helped persuade Trump to back away from his desire to ease social distancing guidelines by Easter Sunday, April 12. Trump extended them until April 30, despite the damage those tactics have done to the U.S. economy.