WASHINGTON — With deaths mounting at the nation’s nursing homes, the White House strongly recommended to governors Monday that all residents and staff at such facilities be tested for the coronavirus in the next two weeks.

Why the government is not ordering testing at the the nation’s more than 15,000 nursing homes was unclear. Nor was it clear why it is being recommended now, more than two months after the nation’s first major outbreak at a nursing home outside of Seattle that eventually killed 43 people.

Vice President Mike Pence, who leads the White House coronavirus task force, told governors on a video conference call that it’s the federal government’s strong recommendation that such testing be done.

“We really believe that all 1 million nursing home residents need to be tested within next two weeks as well as the staff,” added Dr. Deborah Birx, the task force coordinator, according to a recording of the call obtained by the Associated Press.

More than 26,000 residents and staff have died from outbreaks of the virus at the nation’s nursing homes and long-term care facilities, according to an AP tally based on state health departments and media reports. That is about a third of all 76,000 deaths in the U.S. that have been attributed to the virus.

Nursing home operators have said the lack of testing has left them nearly powerless to stop the virus from entering their facilities because they haven’t been able to identity silent spreaders among already sick residents and staff not showing symptoms.

Charlene Harrington, a professor emeritus of nursing at the University of California, San Francisco, said nursing homes should have been prioritized from the start given their vulnerable populations and questioned why the testing recommendation is only happening now.

“We’re two months into it,” she said. “If they had done that to begin with, we would’ve picked up cases early and we wouldn’t have so many deaths.”

Representatives for the federal Centers for Medicare & Medicaid Services did not immediately respond when asked why the agency wasn’t making testing a requirement. In mid-March, it asked homes to cease group gatherings and visitations, and to screen staff with such measures as temperature checks.

A senior administration official defended the government response, saying it told states early in the outbreak to focus on the elderly, helped them secure supplies and that taking a tougher stand with them is still an option.

“If the states aren’t able to come back with plans quickly to do it, then there’s a good chance we will order them to do that, but we believe that right now there are plenty of tests out there,” the officials said on condition of anonymity because he lacked authorization to speak to the media.

Another senior administration official added, “If there needs to be a heavier hand moving into the future, I don’t think there will be, but we’re always prepared to do that.”

Pence led the White House’s weekly call with governors from an isolated room after his press secretary tested positive Friday. Three of the country’s top health care officials, including infection disease expert Dr. Anthony Fauci, are isolating themselves on fears they have been exposed to the virus, too.

Condon reported from New York. Candice Choi in New York and Kevin Freking in Washington contributed to this report.