There is "no evidence" that the 2020 presidential election, the "most secure in American history," was compromised, US election security officials have said, rejecting President Donald Trump's fraud claims.

Republican President Donald Trump has repeatedly made unsubstantiated claims of electoral fraud and has not yet conceded. He has also launched a flurry of legal challenges to projected results in key states won by his Democratic rival Joe Biden.

"There is no evidence that any voting system deleted or lost votes, changed votes, or was in any way compromised," two committees within the Department of Homeland Security that worked on protecting US voting systems affirmed on Thursday.

"When states have close elections, many will recount ballots. All of the states with close results in the 2020 presidential race have paper records of each vote, allowing the ability to go back and count each ballot if necessary," members of committees, which include officials from the Election Infrastructure Government Coordinating Council Executive Committee (GCC)and the Cybersecurity and Infrastructure Security Agency (CISA) said in a joint statement.

"This is an added benefit for security and resilience. This process allows for the identification and correction of any mistakes or errors. There is no evidence that any voting system deleted or lost votes, changed votes, or was in any way compromised," the statement said.

"While we know there are many unfounded claims and opportunities for misinformation about the process of our elections, we can assure you we have the utmost confidence in the security and integrity of our elections, and you should too," the statement added.

CISA, led by the top cybersecurity official, Christopher Krebs, runs a website that debunks misinformation about the election.

The security groups said all the states with close results in the race have paper records of each vote, which can be counted if necessary.

The statement comes as Trump has refused to concede the presidential election to President-elect Biden, baselessly alleging widespread voter fraud, despite presenting no evidence to support such a claim.

Major US media networks called the race for Biden last week. The 77-year-old former vice president holds a near insurmountable lead in both the popular and electoral vote.

Still, Trump and his Republican allies are waging legal challenges in a handful of battleground states and demanding tedious and costly recounts to contest the November 3 election's results.

The defiant Trump campaign is seeking to halt the vote count in Pennsylvania, Michigan and Arizona until they can have partisan poll watchers inspecting the voting process to ensure illegal ballots are not counted.

Biden has 290 electoral votes to Trump's 217. Biden on Thursday won 11 more electoral votes when he won from Arizona, consolidating his lead from 279 to 290. A total of 270 votes out of the 538-member Electoral College votes are needed to secure the presidency.