Donald Trump has insisted he is not conceding the US election, despite seemingly acknowledging for the first time that Democrat Joe Biden won.

“He won because the Election was Rigged,” the Republican president wrote on Twitter, repeating unsubstantiated claims of election fraud.

About an hour later he said he was not conceding the 3 November vote.

He has launched a slew of lawsuits in key states, but has not provided any evidence to back his claims of fraud.

All the lawsuits have so far been unsuccessful.

On Friday, election officials said the vote was the “most secure in American history” and there was “no evidence that any voting system deleted or lost votes, changed votes or was in any way compromised”.

Meanwhile, Mr Biden remains president-elect.

See Also: US election: Sources say Trump give conditions for transfer of power

The Democrat has 306 votes in the electoral college – the system the US uses to choose its president – which far exceeds the 270 threshold to win. Any recounts or legal challenges are not expected to overturn the overall result.

Mr Biden’s lead in the popular vote has also surpassed five million.

Nevertheless, Mr Trump had refused to acknowledge Mr Biden’s victory until – apparently – now.

In a news conference on Friday, Mr Trump said “who knows” which administration would be in power in the future.

His refusal to concede has heightened concerns about the US government’s ability, going forward, to tackle growing Covid-19 infection rates.