"I believe we will prevail! Nevertheless, in the best interest of our Country, I am recommending that Emily and her team do what needs to be done with regard to initial protocols, and have told my team to do the same," he tweeted shortly after GSA released its letter to the Biden team.
"I have dedicated much of my adult life to public service, and I have always strived to do what is right. Please know that I came to my decision independently, based on the law and available facts. I was never directly or indirectly pressured by any Executive Branch official -- including those who work at the White House or GSA -- with regard to the substance or timing of my decision," she said in the letter to Biden.
Murphy was under pressure from Democrats on Capitol Hill, business associations and state and local government leaders to recognize the results of the election and allow Biden's team to begin meeting with counterparts inside the federal government and access additional resources to facilitate the transfer of power.
Several House committees demanded a briefing from Murphy to explain her refusal to acknowledge Biden's victory and threatened to hold a hearing with her when the agency declined to make her available by Monday -- the deadline imposed by lawmakers.
With the GSA's official signoff, Biden and his team can begin accessing classified information, including the Presidential Daily Brief, said Denis McDonough, President Barack Obama's last chief of staff who participated in the Obama-Trump transition.
"It's surely consistent with the spirit and the tradition and the practice of transitions, to make sure that the incoming team is fully briefed on a range of things they're going to confront," he told ABC News ahead of the GSA's announcement Monday afternoon.
While Biden's transition team has been in contact with congressional committees and Democratic leaders about government funding negotiations, and key governors, mayors and vaccine producers on the coronavirus response, there's no substitute for insight into the government from agency officials, he added.
"Best available is the way this has been done in transitions over many decades," said McDonough, who is leading a study of the transition at the University of Notre Dame.
Biden transition official Yohannes Abraham also reacted to the news, calling the decision "a needed step to begin tackling the challenges facing our nation, including getting the pandemic under control and our economy back on track."
"In the days ahead, transition officials will begin meeting with federal officials to discuss the pandemic response, have a full accounting of our national security interests and gain complete understanding of the Trump administration's efforts to hollow out government agencies," he said.
This report was featured in the Tuesday, Nov. 24, 2020, episode of “Start Here,” ABC News’ daily news podcast.
"Start Here" offers a straightforward look at the day's top stories in 20 minutes. Listen for free every weekday on Apple Podcasts, Google Podcasts, Spotify, the ABC News app or wherever you get your podcasts.