President Donald Trump appeared to edge closer towards acknowledging his election defeat to challenger Joe Biden, but then backtracked saying "I concede nothing."

Many of President Trump's tweets over the weekend alleging the US election was rigged against him have been tagged by Twitter as containing
Many of President Trump's tweets over the weekend alleging the US election was rigged against him have been tagged by Twitter as containing "disputed" information. (AP)

President Donald Trump has said he concedes "nothing" after appearing to acknowledge losing the US election, while President-elect Joe Biden has focused on tackling the coronavirus pandemic and set meetings with pharmaceutical companies developing vaccines.

"He won because the Election was Rigged," Trump wrote, not referring to Biden by name, adding a list of complaints about vote counting. 

"NO VOTE WATCHERS OR OBSERVERS allowed, vote tabulated by a Radical Left privately owned company, Dominion, with a bad reputation & bum equipment that couldn't even qualify for Texas (which I won by a lot!), the Fake & Silent Media, & more!"

About 90 minutes later, Trump backtracked, "He only won in the eyes of the FAKE NEWS MEDIA. I concede NOTHING! We have a long way to go. This was a RIGGED ELECTION!"

"WE WILL WIN!" he added.

Biden's victory 

Biden overwhelmed Trump by winning a series of battleground states that the Republican incumbent had won in 2016. 

The Democratic former vice president also won the national popular vote by more than 5.5 million votes or 3.6 percentage points.

Trump had yet to concede the election to Biden who was called as the winner of the election after enough states results came in Biden's favour. 

Biden has won 306 votes in the state-by-state Electoral College system that determines the presidential winner, according to Edison Research, far more than the 270 needed.

READ MORE: Does Trump stand a chance at overturning US election results?

Biden busy with transition efforts

Instead, Trump has spent his days with few public events and pressed unsubstantiated allegations of fraud on social media.

Trump has also stalled the government's normal process of preparing for a new presidential administration, which both Democrats and some Republican have said has serious national security implications.

Trump's campaign team and Republicans have also sought to press their case in court in key battleground states, but have been widely rejected.

Meanwhile, Biden and Vice President-elect Kamala Harris moved forward with their transition efforts, including briefings on the Covid-19 outbreak. 

Ron Klain, Biden's pick for White House chief of staff, urged Trump's administration to allow a seamless transition, calling it vital for national security and combating Covid-19.

The pandemic will be a paramount concern for Biden, who takes office on January 20. 

Klain said Biden's scientific advisors will meet with Pfizer Inc and other drugmakers starting this week to prepare for the "giant logistical project" of widespread vaccination against a virus that has killed more than 245,000 Americans and left millions more unemployed.

READ MORE: Trump appears to hint for first time that Biden could succeed him

Trump supporters rally 

On Saturday, tens of thousands of Trump supporters ventured into Washington to echo his claims of election fraud. 

The "Million MAGA March," referring to Trump's campaign slogan of "Make America Great Again," drew a crowd of flag-waving supporters to downtown Washington.

"Hundreds of thousands of people showing their support in D.C. They will not stand for a Rigged and Corrupt Election!" the president wrote on Twitter, though most crowd estimates were well short of Trump's figure.

READ MORE: Trump loyalists rally in Washington refusing to accept election results

Trump's motorcade passed through the crowd on its way to his golf course in Virginia, producing cheers from demonstrators as the president waved from the back seat.

The march was largely peaceful, though numerous scuffles broke out between Trump supporters and counter-protesters that continued after dark. One person was stabbed and taken to a trauma centre.

Dozens of Proud Boys, a far-right group, marched in the streets, some wearing helmets and ballistic vests, while members of the loose far-left movement known as Antifa staged their own counter-demonstrations.

The city's police force arrested at least 10 people, including several who were charged with assault.

With his chances of reversing the outcome virtually extinguished, Trump has discussed with advisers potential media ventures that would keep him in the spotlight ahead of a possible 2024 White House bid, aides said.

READ MORE: US media project Biden win with 306 electoral votes to Trump's 232

Source: TRTWorld and agencies