WASHINGTON • US Senate Majority Leader Mitch McConnell and other top Republicans have repudiated President Donald Trump's refusal to commit to a peaceful transfer of power, assuring American voters the lawmakers would accept the outcome of November's election.

Mr Trump declined on Wednesday to embrace a peaceful transition in response to a reporter's question and said he expected his election battle with Democrat Joe Biden to be settled by the Supreme Court.

The Republican President's rhetoric on Wednesday, which largely referred to voting by mail, set off a fury that prompted several Republicans in Congress to distance themselves from him.

Despite four years of incendiary statements by Mr Trump, members of his own party have been loath to criticise him, as many feared political retribution.

"The winner of the November 3rd election will be inaugurated on January 20th. There will be an orderly transition just as there has been every four years since 1792," Mr McConnell wrote in a morning tweet on Thursday. Like other Republicans, Mr McConnell did not directly rebuke Mr Trump.

Other Republican leaders were more brusque.

"Fundamental to democracy is the peaceful transition of power; without that, there is Belarus," Republican Senator Mitt Romney tweeted.

A number of Republican leaders joined the effort to quell election fears, including Senators Marco Rubio and House Republican leader Kevin McCarthy, who told reporters: "It will be a smooth transition regardless of the outcome."

Speaking to reporters just hours later on Thursday, Mr Trump doubled down on his stance, repeating baseless assertions that the voting would be a "big scam".

Mr Trump said he did not know that an "honest" election could be held on Nov 3 "with this whole situation, unsolicited ballots".

For months, Mr Trump has cast the November election as being rigged and repeatedly attacked Democrats for promoting widespread use of mail-in ballots for voters who do not want to risk contracting the deadly Covid-19 virus by casting their ballots at potentially crowded polling centres.

Mr Michael Waldman, president of New York University's Brennan Centre for Justice, said voting arrangements were steadily advancing. In an interview with Reuters Television, he added: "The system is not broken. States are actually improving their voting rules day by day."

Democrats accused Mr Trump of threatening American democracy and further politicising his upcoming choice to replace the late Supreme Court Justice Ruth Bader Ginsburg by suggesting the yet-to-be named nominee would have a role in the election's outcome.

Mr Trump, who trails Mr Biden in national opinion polls, has long sought to cast doubt on the legitimacy of the election, asserting without evidence that mail-in voting would be rife with fraud.

"President Trump, you are not a dictator and America will not permit you to be one," said Senate Democratic leader Chuck Schumer, calling him "the gravest threat" to US democracy.

Senator Bernie Sanders, who lost to Mr Biden in the Democratic Party's presidential nominating race, called for an independent commission to oversee the upcoming election.

Democratic House of Representatives Speaker Nancy Pelosi cautioned against panicking over the remarks of a president who she said admires autocratic leaders. At a news conference, she urged Americans to cast their ballots and admonished Mr Trump: "You are not in North Korea, you are not in Turkey, you are not in Russia, Mr President."

REUTERS, NYTIMES, AGENCE FRANCE-PRESSE