Washington — A growing number of states have implemented "shelter in place" orders in response to the coronavirus pandemic, ordering the closure of nonessential businesses and barring residents from making unnecessary trips. But some in Congress believe those closures should not just be ordered on a state-by-state basis, but on a federal level as well.

Democratic Congressman Ro Khanna of California and 19 of his colleagues sent a letter to the White House on Tuesday asking the president to issue a two-week shelter in place order for the entire country.

"We're watching our health care system collapse before us. We're seeing people separated from their loved ones. We're witnessing students shut out from their classrooms and workers let go from their jobs," Khanna told CBS News. "If we want to demonstrate true American leadership and stop this outbreak, we need a nationwide shelter in place order. Let's listen to the experts who are telling us that step is the only way we can truly mitigate the spread of COVID-19. Months of continued half-measures will cost us far more than two weeks of sheltering in place."

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More than 46,000 people have tested positive for the virus in the U.S., and more than 500 people have died. State officials, particularly in New York, have sounded the alarm that an influx in cases could overwhelm hospitals and force some patients to go without treatment, for COVID-19 or other illnesses.

"To effectively slow COVID-19's spread, we must issue a shelter-in-place order for the entire country lasting at least two weeks, excepting only travel for essential services like grocery stores and health care providers, and to and from the workplace for critical workers," the letter said.

At least 15 states have already issued shelter in place orders, including California, the nation's most populous state. Three of the states — Ohio, Indiana and West Virginia — are led by Republican governors.

"Given insufficient availability of mass testing and the ability for asymptomatic individuals to unknowingly spread the coronavirus, we must reduce person-to-person contact to the bare minimum," the lawmakers wrote. "It is the only proven way we can limit the growth of confirmed cases, insulate our health care system, and prevent catastrophe."

President Trump is highly unlikely to order such a directive. He has raised concerns about the impact that "social distancing" will have on the economy, repeatedly saying that "the cure cannot be worse than the problem." Mr. Trump said during a coronavirus task force briefing Monday that his administration will reevaluate the 15-day guideline the White House issued last week when that time is up and he will soon issue new guidelines on how to return to a more normalized workforce and economy.

"Our country wasn't built to be shut down. This is not a country that was built for this. It was not built to be shut down," Mr. Trump said, adding that the U.S. "will soon be open for business."

In the letter to the White House, Khanna acknowledged that "an action of this magnitude will temporarily disrupt daily lives and cause short-term economic pain," but he argued that issuing an order "will help prevent an extended outbreak and response that could plunge us deep into a long-lasting recession."

"As soon as possible, Congress must vote remotely to pass an economic stimulus response bill that will save jobs, replace lost incomes, and lift up all Americans. The cost of preventive action will save trillions of dollars in the long run and many priceless lives," the letter said. Several Democrats in Congress are calling for a change to House rules allow remote voting so lawmakers can continue working while avoiding close contact amid the outbreak.

House Rules Committee Chairman Jim McGovern also said in a new report released Monday night that while there is "no perfect solution" for absent members to vote on the floor, proxy voting — as opposed to remote voting — is "the best of the options available under the circumstances." Proxy voting would allow members to cast votes without traveling back to Washington, D.C.

Khanna's letter concludes that the federal government "must not hesitate."

"If we wait to act until the number of sick and dead reaches a certain threshold, then it will be too late. A state-by-state, locality-by-locality approach is not enough," the letter said.

The request to the White House comes as Senate Democrats negotiate with administration officials to craft a massive stimulus bill. House Speaker Nancy Pelosi introduced her own version of a stimulus package on Monday evening.