(Bloomberg) -- A group of Senate Democrats, including Joe Manchin and Kyrsten Sinema, are demanding answers from President Joe Biden’s White House on its response to the surging Covid-19 pandemic.

A sharply worded letter led by Nevada Senator Jacky Rosen was released Friday as Biden scrambles to address the highly contagious omicron variant, which is overwhelming the nation’s hospitals and leading to a shortage of rapid test kits. It was also signed by Georgia Senator Jon Ossoff and Arizona’s Mark Kelly.

The senators said rising caseloads are straining the healthcare system and the economy.

“We write with grave concern regarding the current state of preparedness and response to the COVID-19 pandemic,” the senators wrote to White House Covid-19 coordinator Jeff Zients. “We ask that you address the steps you have taken to prepare the country for the increase in cases, why the Administration failed to take more significant steps earlier to increase access to at-home tests, and how you plan to mitigate the impact of the current and future variants moving forward.”

The letter seeks answers on the deployment of rapid tests, increase in in-person testing facilities and repair of federal Covid-19 data issues. It cites lines stretching blocks to get Covid testing and the short supply of rapid tests, as well as “hospitals operating under crisis standards of care, health care staff and first responders falling ill, and millions of people who are exhausted from the toll this pandemic has had.” 

It was the third letter this week from a group of congressional Democrats raising alarms about testing shortages, a sign of rising concern about the situation becoming a political liability as the party looks to the midterm congressional elections. 

The White House has moved to ramp up testing availability -- announcing late last month they’d order 500 million tests to give away to Americans before doubling that order this week. Shipments are due to begin later this month. The administration also has increased the number of sites and programs where testing is available.

Private insurers will also, as of Saturday, be required to reimburse Americans for at-home tests that they’ve bought themselves, theoretically reducing the cost to zero for some buyers lucky enough to find them. The White House has also begun setting up free testing sites and pledged 5 million rapid tests to be sent to schools each month.

“It is going to get better and better,” Biden testing coordinator, Tom Inglesby, said in an interview this week. “I can’t tell you the day, but I can tell you it’s going to get better and better.”

The letter also asks the administration to request any additional funding if needed to contain the pandemic. Congressional leaders expect the White House to formally request more funds in the coming weeks but the administration has not yet said whether it will do so. 

Concerns about the administration’s pandemic response have contributed to a precipitous fall in Biden’s approval number in polls and have increased the chances that congressional Democrats lose the House and Senate to Republicans in the November elections. 

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