Joe Biden, the US president-elect, on Tuesday introduced veteran diplomats and policymakers who will make up his national security and foreign policy team, saying: "America is back, ready to lead the world."
Mr Biden, 78, at an event in his home town of Wilmington, Delaware, presented his choices for secretary of state, national security adviser, homeland security secretary, intelligence chief, UN ambassador and climate change envoy.
"It is a team that will keep our country and our people safe and secure," Mr Biden said as the six men and women stood behind him wearing face-masks on the stage of the Queen Theatre.
"It is a team that reflects the fact that America is back, ready to lead the world, not retreat from it."
Mr Biden said that after he is inaugurated on January 20, and Donald Trump leaves the White House, the US will "once again sit at the head of the table, ready to confront our adversaries and not reject our allies".
"These public servants will restore America's global leadership and moral leadership," the former vice president said in a jab at Mr Trump's go-it-alone "America First" policies.
Mr Biden's remarks came shortly after Mr Trump suffered further setbacks in his unprecedented effort to overturn the results of an American presidential election with unsubstantiated claims of fraud.
Pennsylvania and Nevada certified the November 3 election results on Tuesday, a day after the state of Michigan did so, a move which triggered the General Services Administration to launch the transition process.
As more members of his Republican Party came out demanding an end to the impasse, Mr Trump signed off on the GSA move, effectively admitting defeat but still refusing to concede.
"The GSA does not determine who the next President of the United States will be," the president tweeted on Tuesday along with a picture of himself in the Oval Office with the caption: "I concede NOTHING!!!!!"
Mr Trump, 74, who has made few public appearances since his defeat, later attended a traditional Thanksgiving turkey-pardoning event at the White House, touting the Dow breaking 30,000 points and thanking hospital workers battling the Covid-19 pandemic.
He appeared to indirectly address the election at one point, saying: "I say America First, shouldn't go away from that, America First."
The transition formally begins
The GSA determination that Mr Biden is the apparent winner gives the president-elect access to classified briefings on national security threats and will allow his top aides to co-ordinate with federal health officials on addressing the worsening coronavirus pandemic.
Unveiling his Cabinet selections, Mr Biden said he had received calls from world leaders saying they were "looking forward to the United States reasserting its historic role as a global leader".
"This team meets this moment," he said. "They embody my core belief that America is strongest when it works with its allies."
The appointments unveiled by Mr Biden include veterans of the Barack Obama administration and signals a return to traditional US diplomacy and multilateralism.
Antony Blinken, Mr Biden's choice for secretary of state, said the US cannot solve global problems on its own.
"We need to be working with other countries," the former State Department official said. "We need their co-operation. We need their partnership."
Linda Thomas-Greenfield, Mr Biden's choice to be the US ambassador to the UN, echoed those sentiments.
"America is back. Multilateralism is back. Diplomacy is back," said Ms Thomas-Greenfield, a career diplomat.
"The challenges we face – a global pandemic, a global economy, the global climate change crisis, mass migration and extreme poverty, social justice – are unrelenting and interconnected, but they're not unresolvable if America is leading the way."
Former secretary of state John Kerry, who Mr Biden chose as his special envoy on climate change, confirmed the new administration would bring the US back into the Paris climate accord which Mr Trump pulled out of in 2015.
Cuban-born Alejandro Mayorkas was named to head the Department of Homeland Security, whose policing of tough immigration restrictions under Mr Trump was a frequent source of controversy.
Avril Haines was nominated to be the director of national intelligence, the first woman to hold the post, while Jake Sullivan was named national security adviser.
Former Federal Reserve chairwoman Janet Yellen is expected to be named Treasury Secretary, the first woman to hold the job.
With Mr Biden having won a comfortable victory, Mr Trump's last card is to try to disrupt the normally routine process of state-by-state certification of the vote and challenge election results in the courts with claims of irregularities.
The legal efforts have fallen flat, however, along with the attempts to delay state certification.
"The Trump campaign's legal efforts have no basis in fact, no basis in law," said Bob Bauer, a senior adviser to the Biden campaign and a former White House counsel. "Their only purpose is to delay the inevitable.
"Joe Biden won this election and we'll defend this election successfully," he said. "This is not about lawyers, or about partisans, or about Donald Trump's ego or dark fantasies.
"It's about the right to vote and the choice voters made in this election: Joe Biden."