A joint session of Congress will count and confirm electoral college votes, the BBC reported.
Some Republicans have pledged to support Trump’s efforts to overturn the result by formally objecting at the session, in a bid that is almost certain to fail.
Hundreds of National Guard members are being mobilised.
Supporters of Trump have begun gathering in Washington DC to rally against the certification of his defeat, and counter-protests are expected.
In a tweet on Tuesday, Trump announced that he would be speaking at the “SAVE AMERICA RALLY” the following day.
He has refused to concede the November 3 election, repeatedly alleging fraud without providing any evidence.
Biden, a Democrat, is due to be inaugurated as president on January 20.
The two houses of Congress – the House of Representatives and the Senate – will hold a joint session on Wednesday, where they will open sealed certificates from the US’ 50 states containing a record of their electoral votes.
Under the US system, voters cast their ballots for “electors”, who in turn formally vote for the candidates weeks after the election. Biden received 306 votes under the electoral college system, to Trump’s 232.
Bipartisan representatives from the two chambers will read out the results on Wednesday and do an official count.
There is a split in the Republican party, with dozens of House Republicans and a smaller group of Senators expected to object to the count from some of the key swing states.
Ted Cruz is leading a group of about a dozen senators calling for a 10-day delay to audit unsubstantiated allegations of election fraud.
Vice-President Mike Pence – who as president of the Senate is due to oversee the session and declare Biden the winner – said he welcomed the move.
He stopped short of repeating allegations of fraud but his chief of staff said Pence shared what he called “the concerns of millions of Americans about voter fraud and irregularities”.
By US election law, Pence’s duty in the proceedings is purely administrative, but Trump has urged his vice-president to “come through”.