(CNN) — Florida is the only state that has not yet submitted a plan to the US Department of Education for how it will use federal Covid-19 relief funds for schools, according to a new letter from the agency — the latest in a series of escalating stances against the Biden administration.

The US Education Department sent a letter to Florida Education Commissioner Richard Corcoran on Monday inquiring about the status of the state’s plan and underscoring it is needed to unlock more than $2.3 billion in remaining American Rescue Plan funds.

“The U.S. Department of Education (Department) has now received an ARP ESSER State plan from 51 of 52 State educational agencies (SEAs), with the exception of the Florida Department of Education,” wrote Ian Rosenblum, the acting assistant secretary for the agency’s Office of Elementary and Secondary Education.

The Florida Education Department’s “failure to meet its responsibilities is delaying the release of essential ARP ESSER resources that are needed by school districts and schools to address the needs of students most impacted by the pandemic,” Rosenblum noted in the letter.

The letter comes as the Biden administration and Gov. Ron DeSantis have sparred on Covid-19 and other key issues on the national political stage. The Republican governor has taken a hard stance against statewide school mask mandates, as schools across the country grapple with how to provide safe, in-person instruction for all students while families await vaccine approval for children under 12.

The US Education Department recently repaid a group of Florida school board members whose salaries had been withheld for implementing mask mandates in defiance of the governor’s executive order that parents, not school officials, decide how to protect their children in the pandemic. And last month, the department’s civil rights enforcement arm said it was opening an investigation into whether the Florida Education Department “may be preventing school districts in the state from considering or meeting the needs of students with disabilities” with the mask mandate ban.

In an effort to help states reopen schools safely during the pandemic, the Biden administration earlier this year announced the allocation of more than $122 billion in Covid relief for pre-K to 12 schools, with two-thirds of those funds — totaling $81 billion — “made available to states immediately.” The remaining federal dollars are contingent on the approval of a state plan detailing how the funds will be used, the US Education Department said.

Florida was allocated more than $7 billion as part of that funding to support “students’ health and safety and address their social, emotional, mental health, and academic needs in response to the COVID-19 pandemic,” Rosenblum noted, and two-thirds of that allocation was released in March.

But the remaining third, totaling more than $2.3 billion, has not yet been released because Florida failed to meet a June deadline for submitting its state plan, the letter explained. The state also missed “July and August submission timelines that were anticipated following conversations with your staff,” Rosenblum wrote to Corcoran.

In a statement to CNN on Monday, the Florida governor’s office said that “at this time, no district has articulated a need for funding that cannot be met with currently available resources. Whenever this may change in the future, the state of Florida will coordinate with USDOE to ensure Florida students and educators have all the resources they need.”

Monday’s letter also noted that Florida’s Education Department has drawn down some of the American Rescue Plan funds at the state level but has not yet awarded funds to local agencies.

“We appreciate that FDOE recognizes the need for the vital resources that the ARP Act provides, as demonstrated by FDOE’s draw-down of more than $177 million in ARP ESSER funds to date for use at the State level. Yet we have heard repeatedly from parents, teachers, and superintendents from school districts in Florida that FDOE has not yet awarded ARP ESSER funds to local educational agencies,” wrote Rosenblum.

“FDOE’s delay raises significant concerns because of the unnecessary uncertainty it is creating for school districts across the State and because it is hindering their ability to confidently plan for how to use these funds to address the needs of students,” the department official added.

Rosenblum pledged in the letter that the US Education Department “remains ready to provide any support” that Florida officials may need to advance a state plan.

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