The General Services Administration is tasked with formally recognizing Joe Biden as president-elect, which begins the transition. But the agency's Trump-appointed administrator, Emily Murphy, has not started the process and has given no guidance on when she will do so.
That lack of clarity is fueling questions about whether Trump, who has not publicly recognized Biden's victory and has falsely claimed the election was stolen, will impede Democrats as they try to establish a government.
There is little precedent in the modern era of a president erecting such hurdles for his successor. The stakes are especially high this year because Biden will take office amid a raging pandemic, which will require a comprehensive government response.
"America's national security and economic interests depend on the federal government signaling clearly and swiftly that the United States government will respect the will of the American people and engage in a smooth and peaceful transfer of power," Jen Psaki, a Biden transition aide, tweeted Sunday.
The advisory board of the nonpartisan Center for Presidential Transition also urged the Trump administration to "immediately begin the post-election transition process and the Biden team to take full advantage of the resources available under the Presidential Transition Act."
Biden, who was elected the 46th president on Saturday, is taking steps to build a government despite questions about whether Trump will offer the traditional assistance.
He is focusing first on the virus, which has already killed nearly 240,000 people in the United States. Biden on Monday announced details of a task force that will create a blueprint to attempt to bring the pandemic under control that he plans to begin implementing after assuming the presidency on Jan. 20.
Former Surgeon General, Dr. Vivek Murthy, ex-Food Drug Administration Commissioner Dr. David Kessler and Dr. Marcella Nunez-Smith, a Yale University associated professor and associate dean whose research focuses on promoting health care equality for marginalized populations, are its co-chairs.
"Dealing with the coronavirus pandemic is one of the most important battles our administration will face, and I will be informed by science and by experts," Biden said in a statement. "The advisory board will help shape my approach to managing the surge in reported infections; ensuring vaccines are safe, effective, and distributed efficiently, equitably, and free; and protecting at-risk populations."
There are also 10 members, including two former Trump administration officials: Rick Bright, who said he was ousted as head of the Biomedical Advanced Research and Development Authority after criticizing the federal government's response to the coronavirus, and Luciana Borio, who until last year was a biodefense specialist on the National Security Council.
The remainder of the panel includes experts with expertise in a number of areas, including Eric Goosby, who was then-President Barack Obama's global AIDS coordinator.
Biden was also launching agency review teams, groups of transition staffers that have access to key agencies in the current administration. They will collect and review information such as budgetary and staffing decisions, pending regulations and other work in progress from current Trump administration staff at the departments to help Biden's team prepare to transition.
But that process can't begin in full until the GSA recognizes Biden as president-elect. The definition of what constitutes a clear election winner for the GSA is legally murky, making next steps unclear, especially in the short term.
The GSA's leadership is supposed to act independently and in a nonpartisan manner, and at least some elements of the federal government already have begun implementing transition plans. Aviation officials, for instance, have restricted the airspace over Biden's lakefront home in Wilmington, Delaware, while the Secret Service has begun using agents from its presidential protective detail for the president-elect and his family.
There were other signs that some leaders were preparing for a new administration.
Biden aides said the president-elect and transition team had been in touch with Republican lawmakers. Israel's prime minister, Benjamin Netanyahu, one of Trump's closest allies, opened a Cabinet meeting on Sunday by congratulating Biden, a former vice president and longtime senator.
"I have a long and warm personal connection with Joe Biden for nearly 40 years, and I know him as a great friend of the state of Israel," Netanyahu said.
George W. Bush, the only living Republican former president, called Biden "a good man, who has won his opportunity to lead and unify our country."
But other Republicans, including Sen. Lindsey Graham of South Carolina, urged Trump to continue pursuing legal challenges related to the election, making a bumpy transition more likely.
Biden started his first full day as president-elect on Sunday by attending church at St. Joseph on the Brandywine near his home in Wilmington, as he does nearly every week. After the service, he visited the church cemetery where several family members have been laid to rest, including his son Beau.
He otherwise spent most of the day inside his home while some of his staff spent hours on a conference call focused on transition planning.
Those plans also may hinge on two Senate races in Georgia that have advanced to a Jan. 5 runoff. If Republicans hold those seats, they'll likely retain the Senate majority and be in a position to slow confirmation of Biden's top Cabinet choices and complicate his legislative goals, including sweeping calls for expanding access to health care and bolstering the post-pandemic economy with green jobs and infrastructure designed to combat climate change.
That could test Biden's campaign pledge to move past the divisiveness of the Trump era and govern in a bipartisan manner.
While Biden's aides acknowledged it would be easier for him to get his proposals enacted with Democrats controlling the Senate, Stef Feldman, the policy director on his campaign, said Biden has been known in the past for working with Republicans to move legislation.
"The president-elect's plan will remain the president-elect's plans regardless of who wins the Senate majority, and he will work with colleagues across the aisle in order to get it done," she said.
During his victory speech on Saturday, he vowed to be a president who "seeks not to divide, but unify" and appealed to Trump supporters to "give each other a chance."
Those close to Biden say he will navigate the period ahead by harnessing his sense of empathy that became a trademark of his campaign. Biden often spoke of the pain he experienced following the death of his wife and young daughter in a 1972 car crash, and Beau's 2015 death due to brain cancer.
"My brother knows how to feel," said Valerie Biden Owens, Biden's sister and longtime top adviser. "Joe's strength has been resilience and recovery and that's what we need as a country."
By Will Wissert/AP