A Justice Department official confirmed Monday evening that Richard Pilger, a career official who was serving as director of the Elections Crimes Branch, has resigned from his role in the division because of the attorney general's memo authorizing U.S. attorneys to "pursue substantial allegations of voting and vote tabulation irregularities," despite little evidence surfacing thus far of any widespread voter fraud in the 2020 election. 

Pilger has stepped back into a role in the DOJ's Public Integrity Section. 

The New York Times reported that Pilger wrote to colleagues in an email this evening, "Having familiarized myself with the new policy and its ramifications, I must regretfully resign from my role as director of the Election Crimes Branch.”

A DOJ spokesperson did not respond to a request for comment on Pilger's resignation. 

When ABC News sought a response from Pilger, an automatic reply to the email said, "I am no longer the Director of the Election Crimes Branch, and have stepped back to the line at the Public Integrity Section."

-ABC News' Alexander Mallin

The Biden transition team will not receive full intelligence briefings until the General Services Administration officially "ascertains" the former vice president to be winner of the presidential election, according to a statement from the Office of Director of National Intelligence on Monday. 

"ODNI follows the statutory direction provided in the Presidential Transition Act, which requires ascertainment of the candidate by the administrator of GSA prior to supporting a potential presidential transition. ODNI would not have contact with any transition team until notified by the GSA Administrator," an ODNI spokesperson said in a statement.

Meanwhile, outside government watchdogs are already warning that a continued delay in briefings could carry grave national security implications for the incoming administration. 

Aaron Scherb, the legal director at Common Cause, told ABC News on Monday that the "petty and unproductive" decision by GSA to withhold key resources to the Biden transition could have the "potential for catastrophic results." 

"By GSA not signing off on this, there is certainly some classified intelligence information that the incoming administration would not have access to -- and would potentially not be fully prepared on day one to be able to counteract ongoing efforts from our adversaries like all previous incoming administrations have," Scherb said. 

"If the Biden transition team doesn't have access to some of the documents and information," he continued, "there are national security concerns."

-ABC News' Molly Nagle and Lucien Bruggeman

Attorney General William Barr sent a memo to U.S. attorneys Monday evening authorizing them to "pursue substantial allegations of voting and vote tabulation irregularities," despite little evidence surfacing thus far of any widespread voter fraud in the 2020 election. 

In the memo Barr says that such inquiries "may be conducted if there are clear and apparently-credible allegations of irregularities that, if true, could potentially impact the outcome of a federal election in an individual State." 

But Barr emphasized in the letter that this should not be taken as the DOJ believing there was widespread fraud -- a baseless claim being made by attorneys for Trump and the RNC. Rather, he's doling authority out to U.S. attorneys in the event they might uncover any such credible evidence of a fraud conspiracy that might affect vote tabulations before election results are certified.

"Nothing here should be taken as any indication that the Department has concluded that voting irregularities have impacted the outcome of any election," Barr wrote. "Rather, I provide this authority and guidance to emphasize the need to timely and appropriately address allegations of voting irregularities so that all of the American people, regardless of their preferred candidate or party, can have full confidence in the results of our elections." 

"While it is imperative that credible allegations be addressed in a timely and effective manner, it is equally imperative that Department personnel exercise appropriate caution and maintain the Department's absolute commitment to fairness, neutrality and non-partisanship," Barr said in the memo. "While serious allegations should be handled with great care, specious, speculative, fanciful or far-fetched claims should not be a basis for initiating federal inquiries."

-ABC News' Alexander Mallin

Biden is slated to give remarks focused on the Affordable Care Act and the Trump administration's lawsuit to overturn it. Biden will talk about his own plan "to expand access to quality, affordable health care."

The event in Wilmington, Delaware, is slated for 2 p.m.

The Supreme Court is scheduled to hear arguments at 10 a.m. in the case brought by Trump and 18 Republican-led states asking that the Affordable Care Act be eliminated in its entirety.

Former President Barack Obama "spoke separately this afternoon with president-elect Joe Biden and vice president-elect Kamala Harris," an Obama spokesperson said. "He congratulated them on their historic victory and told them how proud he was of the campaign they ran in unprecedented times.”

Obama said in a statement Saturday that he "couldn't be prouder" of Biden and Harris.

"We’re fortunate that Joe’s got what it takes to be President and already carries himself that way. Because when he walks into the White House in January, he’ll face a series of extraordinary challenges no incoming President ever has – a raging pandemic, an unequal economy and justice system, a democracy at risk, and a climate in peril," Obama said.

"I know he’ll do the job with the best interests of every American at heart, whether or not he had their vote. So I encourage every American to give him a chance and lend him your support. The election results at every level show that the country remains deeply and bitterly divided," he said.

"Our democracy needs all of us more than ever," Obama said. "And Michelle and I look forward to supporting our next President and First Lady however we can."

Former President Jimmy Carter said in a statement, "Rosalynn joins me in congratulating our friends President-elect Joe Biden and Vice President-elect Kamala Harris. We are proud of their well-run campaign and look forward to seeing the positive change they bring to our nation."

Former President Bill Clinton tweeted, "America has spoken and democracy has won. Now we have a President-Elect and Vice President-Elect who will serve all of us and bring us all together. Congratulations to Joe Biden and Kamala Harris on your momentous victory!