A federal prosecutor on Thursday agreed to postpone the deadline for North Carolina election officials to turn over millions of voting records to Immigration and Customs Enforcement, after election officials balked at the sweeping request two months before the midterm elections.

Federal prosecutors in the Eastern District of North Carolina, working in conjunction with ICE, subpoenaed the state and 44 counties last Friday, seeking an estimated 20 million documents. The subpoenas included at least five years of ballots and eight years of voter registration applications, provisional voting forms, absentee request forms, voter registration cancellations, and "any and all" inquiries sent to voters asking them to confirm their citizenship.

The subpoena originally asked that the documents be produced by September 25, but the state said complying would cripple its ability to perform "critical tasks" related to November's elections.

Assistant U.S. Attorney Sebastian Kielmanovich agreed Thursday to postpone compliance until January 2019 in a letter to North Carolina's State Board of Elections, which provided the letter to NBC News. In the letter, Kielmanovich said the timing of the request was initially designed to prevent records from being destroyed, and made the delay conditional on preservation of those documents.

The breadth of the request — "the most exhaustive on record," Josh Lawson, general counsel for the State Board of Elections, wrote of the subpoenas sent to the counties in an email to Kielmanovich — and the timing stirred alarm among voting rights advocates, who feared it would hamstring election officials at a critical time and expose private voter information.

In Thursday's letter agreeing to a postponement of subpoena compliance, Kielmanovich wrote that prosecutors would be willing to discuss narrowing the scope of the subpoena, noting that they may not need all voter ballots. He added that his office wanted information to be redacted so voter's choices were not included.

“Promises of a future negotiation…aren’t enough to satisfy me as a North Carolina voter,” said Allison Riggs, senior attorney focused on voting rights at the North Carolina-based Southern Coalition for Social Justice.

Justin Levitt, a former Deputy Assistant Attorney General in the Department of Justice who worked on voting rights cases in the Obama administration, said the broad nature of the request smacked of a fishing expedition.

"It's nuts," Levitt said. “It’s the equivalent of asking, in order to investigate bank fraud, asking the ten largest banks for all of their bank records pertaining to anybody. That’s not how you’d investigate a bank fraud."

Levitt, now a professor a Loyola Law School, said ICE involvement on isolated cases of voter fraud is normal and often done in the course of immigration investigations, but a widespread voter fraud investigation would be unusual. What's more, he noted, large-scale election investigations are typically done by the Department of Justice, not a U.S. attorney's office.

Critics also raised concerns that the prosecutors and ICE were seeking information that the president’s voter fraud commission, co-chaired by Vice President Mike Pence and Kansas Secretary of State Kris Kobach, sought before being disbanded earlier this year, including voter registration information.

“It looks to me like the now defunct and discredited Pence-Kobach commission has been reincarnated,” Riggs said.

Asked about the reason for the subpoenas, an ICE spokesman they could not comment on ongoing federal investigations, but pointed to the Eastern District of North Carolina's announcement last week of 19 indictments of foreign nationals for illegally voting in North Carolina's 2016 elections.

The Southern Coalition for Social Justice is preparing a legal memo to encourage state officials to fight the subpoena's requests in court. North Carolina's State Board of Elections will meet on Friday, where they are expected to discuss the subpoena.

If the state does not try and oppose the subpoena, Riggs said, her group will do so.

North Carolina’s state’s election board did an audit for voter fraud after the 2016 election. Out of the nearly 4.8 million people who cast a ballot, state election officials found 41 confirmed noncitizen voters and 441 ineligible voters with disenfranchising felony convictions.

Voter education, they wrote in a report, was the issue — not intentional fraud, and they vowed to improve warnings on forms and poll worker education.