US President-elect Joe Biden has unveiled officials for six important posts, as he prepares to take office.
Mr Biden said that "America is back" and "ready to lead the world, not retreat from it".
If confirmed, Avril Haines would be the first female director of national intelligence and Alejandro Mayorkas the first Latino homeland security boss.
President Trump has agreed transition moves must start and Mr Biden will now get a top secret intelligence brief.
However, Mr Trump still refuses to concede the election and continues to repeat unsubstantiated claims that the 3 November vote was "rigged".
The White House said Mr Biden would get the Presidential Daily Brief, the document that updates the president on details of the latest international threats and developments.
And following approval from the General Services Administration (GSA), Mr Biden can now access key government officials and millions of dollars in funds as he prepares to take over on 20 January.
On Tuesday, Governor Tom Wolf said he had certified Mr Biden's victory in Pennsylvania, a key swing state. Another, Michigan, certified the same outcome on Monday.
Speaking in Wilmington, Delaware, on Tuesday, the president-elect highlighted the need to rebuild alliances, as well as tackling coronavirus and climate change.
He said his team would "tell me what I need to know, not what I want to know".
The appointments suggest a move away from the "America First" narrative of President Trump.
"We cannot meet these challenges with old thinking and unchanged habits," Mr Biden said.
The president-elect also noted that he was struck by his calls with world leaders "by how much they're looking forward to the United States reasserting its historic role as a global leader over the Pacific, as well as the Atlantic, all across the world".
He later told reporters he spoke with Prime Minister Boris Johnson and other leaders about the Ireland and Northern Ireland border.
Mr Biden, who has Irish heritage, said he was against a guarded border, and said it must be kept open. "The idea of having the border north and south once again being closed, it's just not right."
In an interview with NBC News, Mr Biden emphasised the outreach from the administration "has been sincere" and not "begrudging".
Mr Biden also said there were plans for him to meet with the Covid task force in the White House regarding vaccine distribution and access.
"We're gonna not be so far behind the curve as we thought we might be," he said.
Mr Biden presented six key figures on Tuesday:
One choice that is expected but has not been announced yet is former Federal Reserve chair Janet Yellen as treasury secretary
Most of the picks, although not Mr Kerry or Mr Sullivan, will need confirmation by the Senate. Rejection of a nominee is rare. The last was in 1989, although some nominees have withdrawn from consideration.