Biden Photo: AFP

 US President-elect Joe Biden on Tuesday introduced a slate of veteran diplomats and policy-makers who will make up his national security and foreign policy team, saying, "America is back, ready to lead the world."

Biden, 78, presented his picks for secretary of state, national security advisor, homeland security secretary, intelligence chief, UN ambassador and climate change envoy.

"These public servants will restore America's global leadership and moral leadership," Biden said as the six men and women stood behind him wearing face masks.

Biden said that after he is inaugurated on January 20 and President 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."

"It is a team that reflects the fact that America is back, ready to lead the world, not retreat from it," he said in a jab at Trump's go-it-alone "America First" policies.

Biden's remarks came ­after Trump suffered further setbacks in his efforts to overturn the results of the 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 (GSA) to launch the transition process.

As more members of his Republican Party came out demanding an end to the impasse, Trump signed off on the GSA move, effectively admitting defeat. But on Tuesday he tweeted a picture of himself in the Oval Office with the caption "I concede NOTHING!!!!!"

The 74-year-old Trump later attended a traditional Thanksgiving turkey-pardoning event at the White House.

He appeared to indirectly address the election, saying, "I say America First - shouldn't go away from that."

The GSA determination gives Biden access to classified information and will allow his aides to coordinate with officials on addressing the worsening coronavirus pandemic.

"We're already working out meeting with the COVID team in the White House... The outreach has been sincere," Biden told NBC in his first TV interview since winning the presidency.

The slate that Biden unveiled included veterans of the Barack Obama administration and signaled a return to traditional US diplomacy and multilateralism.

Biden said that "America's going to reassert its role in the world and be a coalition ­builder," but he denied it would be like a third term of Obama - whom he served as vice president.

"We face a totally different world," the president-elect said. "President Trump has changed the landscape. It's become America First, which meant America alone."