Updated 5/29/20 with response from the Pentagon.

WASHINGTON ― The Pentagon has spent less than a quarter of the $10.6 billion Congress gave it in March to protect military personnel and marshal American industry to procure face masks, ventilators and other products hospitals need in their fight against the coronavirus.

Citing the Trump administration’s most recent reports to Congress, Democratic senators say the Pentagon has placed on contract 23 percent of the funds it was provided nine weeks ago as part of the Coronavirus Aid, Relief, and Economic Security Act of 2020. It’s the latest criticism in a sharp back and forth between congressional Democrats and the Pentagon over the latter’s response to the global pandemic.

As the nation surpassed 100,000 deaths from COVID-19, nine Senate Democrats wrote to Defense Secretary Mark Esper on Thursday, calling for him to provide Congress with a spending plan for the remaining funds. Defense Appropriations Subcommittee Vice Chairman Dick Durbin, D-Ill., led the letter, which was obtained by Defense News.

“We are concerned by the delays in providing this important information, the lack of transparency in the use of emergency funds appropriated to the Department, and troubling signs the funds will instead be spent for other purposes,” the letter read. “Lacking a spend plan, we are not even sure what those purposes may be.”

Senate Appropriations Committee Vice Chairman Patrick Leahy, D-Vt., and Senate Armed Services Committee ranking member Jack Reed, D-R.I., signed the new letter with Durbin, Sens. Dianne Feinstein, D-Calif.; Patty Murray, D-Wash.; Jon Tester, D-Mont.; Tom Udall, D-N.M.; Brian Schatz, D-Hawaii; and Tammy Baldwin, D-Wis.

Though the coronavirus rescue package included more than $1 billion for National Guard deployments requested by the administration to support state authorities, the Guard didn’t need the money because the Federal Emergency Management Agency has since taken responsibility for reimbursing states. “We do not understand why the Department requested these funds … nor do we know what they will be used for now,” the lawmakers wrote.

The Pentagon has thus far obligated $167 million of the $1 billion Congress granted under the Defense Production Act, a Korean War-era law that the president recently invoked, to have industry produce key items such as N95 respirator masks and swabs needed for coronavirus testing, ventilators and other items.

“Lacking further information from the Department on its plans for these funds, we are unable to answer simple questions such as whether the U.S. Government is doing everything in its power to address shortfalls in supplies which are not only needed at this moment, but also in preparation for a predicted second wave of coronavirus infections,” the lawmakers wrote.

In a statement, chief Pentagon spokesman Jonathan Rath Hoffman said the department “remains committed to legally and responsibly executing these funds on the highest priorities to protect our military and their families and safeguard our national security capabilities. As we have seen, this is an evolving and dynamic situation where priorities and requirements change, which is why it is so important that we remain faithful and accountable stewards of the taxpayer dollar.”

“As the Members know, the spend plan is due per the CARES Act in four weeks, on June 26th. The plan is currently in final review and approval, and we expect it to be on the Hill by close of business [May 29], a full month prior to the required due date,” Hoffman added.

“In the interim, the Department has shown its commitment to transparency through daily and weekly updates from senior DoD leaders to multiple Congressional committees — both staff and members. In addition, DoD has provided hundreds of responses to Congressional COVID queries, and will continue to do so.”

The Department of Defense announced its first use of the Defense Production Act on April 13 in the form of $133 million in contracts to 3M, O&M Halyward, and Honeywell to boost domestic production of N95 respirator masks.

On Thursday, the DoD announced its latest: $2.2 million to Hollingsworth & Vose for 27.5 million N95 ventilator filters and 3.1 million N95 respirators per month, starting in August ― all to “relieve manufacturing bottlenecks and will expand N95 mask production and ventilator use.”

The letter comes just weeks after the Pentagon made a surprise decision to move its point person for the Defense Production Act, Jen Santos, into a new job. But it’s also as Democrats have urged President Donald Trump to dramatically increase domestic production of personal protective equipment and testing supplies.

“Throughout this crisis, you have continued to lay blame for the public health response on others, from members of the previous administration to those who report to you now,” Schatz, Durbin, Tester and Baldwin wrote in a letter to Trump on May 15. “Your dismissal of the Pentagon’s senior industrial policy official appears to be the latest example of removing a knowledgeable and well-regarded technocrat for no reason but to cover for your failure to fully invoke and utilize the DPA authorities.”

In early May, Esper clapped back at accusations the DoD had not been transparent in its response to COVID-19. A letter from Senate Armed Services Committee member Elizabeth Warren, D-Mass., and nine Democratic colleagues, which accused the Defense Department of failing to adequately respond to the pandemic, contained “a number of misleading, false, or inaccurate statements,” Esper said.

“Our commitment is to ensure that we provide Congress complete, accurate and timely information which we are doing on weekly basis,” he said, adding that he speaks with committee leaders on a weekly basis. “We recognize Congress has an important oversight role, but it should be an informed oversight role, and we are committed to doing that.”

Aaron Mehta contributed to this report.