Sunday, US President-elect Joe Biden began the first steps toward moving to the White House in 73 days, at a time when Donald Trump still refused to admit defeat and tries to raise doubts about the election results.

As congratulations poured in from world leaders and supporters after a night of celebrations, Biden and Vice President-elect Kamala Harris announced that they would receive a joint briefing Monday in Wilmington, Delaware, from their transition advisory team on COVID-19.

After that, Biden will make statements about the coronavirus and the economic recovery.

The President-elect and Vice President also launched a transitional website BuildBackBetter.com and a Twitter account @Transition46 regarding the transition.

Meanwhile, Trump played golf at a course near Washington, the same place he was Saturday when Biden was announced winning enough votes to become president.

"Since when will the media announce who will be our next president?" Trump wrote on Twitter Sunday.

Trump, who has not announced scheduled public meetings on his program Monday, plans to file a series of lawsuits next week, according to his lawyer, Rudy Giuliani, who said he had "a lot of evidence" of electoral fraud.

However, former Republican President George W. Bush confirmed in a statement that "the result is clear," adding that he had called "the president-elect" Biden and Harris to congratulate them.

"The American people can be confident that these elections were basically fair ... We must unite for the sake of our families and our neighbors, for the sake of our nation and its future," Bush said.

Biden's transitional website published four priorities that the president-elect will work on: COVID-19, economic recovery, racial equality and climate change.

"The team that is being assembled will face these challenges from day one," the site said, referring to January 20, 2021, the day he assumed power as the 46th President of the United States.

Biden, who will turn 78 on November 20, is the oldest person to be elected to the White House. Harris, 56, a senator from California, is the first woman, the first black person, and the first person of South Asian descent to be elected vice president.

Biden intends to appoint a task force Monday to address the COVID-19 pandemic, which has killed more than 237,000 people in the United States and is resuming the outbreak across the country.

The President-elect also intends to return the United States to the Paris Climate Agreement and to abolish the immigration decree that prohibits the entry of citizens of several Muslim-majority countries into the United States.

Biden has pledged to choose a government that reflects the country's diversity, although he may struggle to get approval for more progressive appointments if Republicans retain control of the Senate. The majority in the Senate has not yet been decided, as it is still awaiting two races in Georgia in January.

- "Accept the inevitable" -

Biden, the second Catholic to be elected president of the United States after John F. Kennedy, attended Sunday morning mass at a church in his hometown of Wilmington, Delaware.

He also visited the grave of his son Bo Biden, who died of brain cancer in 2015, and the graves of his first wife and daughter, who died in a car accident in 1972.

The Trump campaign spoke about legal objections to the results in several states, but no evidence has yet emerged of any violations that would affect the results.

Giuliani's attorney told a Fox News program that Trump's team will file a lawsuit in Pennsylvania on Monday against officials "for violating civil rights, holding unfair elections and violating state law."

"The first case will be in the state of Pennsylvania. The second will be either Michigan or Georgia," Giuliani said, noting that the files will be prepared during the next week.

First lady Melania Trump tweeted Sunday, "The American people deserve fair elections. Every vote should count as legal, not illegal."

In an interview on CNN Sunday, Biden's chief adviser Simon Sanders rejected the judicial appeals that Trump's team intends to present, describing them as "baseless legal strategies."

Biden won nearly 74.6 million votes compared to 70.4 million for Trump, and 279 votes in the electorate that determines who will be president in exchange for 214 for Trump.

The counting of votes has not yet ended in Arizona, where Biden is also leading, and if he wins, that means he will receive an additional 11 votes in the Electoral College. It also leads in Georgia which has 16 votes. If he wins both, he will end up with 306 votes, the same tally that Trump won in 2016 when he ousted Hillary Clinton.

Only two Republican senators, Mitt Romney and Lisa Murkowski, congratulated Biden on the victory.

Representative James Cleburn of South Carolina said the Republican Party had a "responsibility" to help convince Trump that it was time to give up.

Romney stated that the president "will ultimately accept the inevitable."

He added that he would prefer to see the world watch a more graceful departure, but this is not the nature of a man.

- "Do not give up, Mr. President."-

For his part, Republican Senator Lindsey Graham told Fox News Sunday, addressing Trump, "Do not give up anything, Mr. President, fight hard."

"We will work with Biden if he wins, but Trump did not lose," he said.

In his Saturday victory speech, Biden promised to unite the sharply divided nation. Regarding Trump's supporters, he said, "These are not our enemies. They are Americans," and "Let us begin here today, the end of this era of demonization in America."

Financial markets welcomed Biden's victory, as stocks rose in Tokyo and Hong Kong, and US futures rose on Wall Street on Sunday.

The leaders of Britain, France, Germany, Italy, Spain and other European countries extended their congratulations to Biden, along with Australia, Canada, India, Indonesia, Israeli occupation, Japan, South Korea and several Arab countries.