President Trump has so far refused to accept Mr Biden’s election victory. But a letter sent by GSA Administrator Emily Murphy and obtained by CNN shows the first signs that Mr Trump’s team could be accepting defeat.
Taking to Twitter, President Trump thanked Ms Murphy from the General Services Administration (GSA).
But he warned that his case to challenge the election results “strongly continues”.
Mr Trump wrote: “I want to thank Emily Murphy at GSA for her steadfast dedication and loyalty to our Country.
“She has been harassed, threatened, and abused – and I do not want to see this happen to her, her family, or employees of GSA. Our case STRONGLY continues, we will keep up the good fight.
“And 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.”
It comes more than two weeks after President-elect Biden was declared the winner of the election.
Ms Murphy said she had not been forced by the White House to delay the formal transition.
She also insisted that she did not make a decision “out of fear or favouritism”.
In the letter, Ms Murphy wrote: “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.
“To be clear, I did not receive any direction to delay my determination.”
She added: “Even in the face of thousands of threats I have remained committed to upholding the law.”
Analysts have called the letter “as near as we’ve had to a concession” from President Trump’s team.
The move will let the transition of power begin by allowing the current administration team to coordinate with the incoming Biden officials.
It also provides millions of US government funding for the transition process.
Mr Biden already started preparations for his presidency before the letter was released.
On Monday, Mr Biden announced several of his cabinet picks which will make up his administration.
The delay in formalising the transition meant that Biden’s team could not access government data or spend the $6.3 million (£4.7 million) now available.
Mr Biden’s team welcomed the decision to allow the transition to begin.
In a statement it said: “Today’s decision is a needed step to begin tackling the challenges facing our nation, including getting the pandemic under control and our economy back on track.
“This final decision is a definitive administrative action to formally begin the transition process with federal agencies.”