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.

Biden warns of 'dark winter' ahead as he lays out COVID-19 plan, calls for unity on masks

President-elect Joe Biden in his first solo remarks to Americans since his victory speech over the weekend reminded Americans of the ongoing coronavirus pandemic as cases and hospitalizations rise across the country, and said the country is “still facing a very dark winter” before offering his plan to combat it.

"We are ready to get to work addressing the needs of the American people. Today, that work begins," Biden said from The Queen Theater in Wilmington Delaware, following a briefing with his newly-announced COVID-19 advisory board. "It starts with doing everything possible to get the COVID-19 under control, so that we can reopen our businesses safely and sustainably, resume our lives, put this pandemic behind us."

While he praised the announcement from Pfizer Monday morning that the company has a vaccine in trial that looks "90% effective in preventing COVID-19," Biden reminded that even if the vaccine is approved, it will not be widely available for months. He went on to urge all Americans, regardless of whether they voted for him, to "end the politicization of basic responsible public health steps."

"This election is over. It’s time to put aside the partisanship and the rhetoric that’s designed to demonize one another," Biden said, reminding Americans to keep social distancing and wearing a mask.

"Doesn't matter who you voted for, whether you stood, where you stood before election day, doesn't matter your party, your point of view. We can save tens of thousands of lives if everyone would just wear a mask for the next few months. Not Democrat or Republican lives, American lives," he added. "A mask is not a political statement but it is a good way to start pulling the country together."

After pledging to rejoin the World Health Organization on "Day One," Biden also said his advisory board will include experts on global health security, "so that we can restore U.S. global leadership to fight this pandemic" -- in sharp contrast to Trump's isolationist approach to the virus and general policy.