Explainer - The meeting of the US Congress that will seal Biden's win

Here's what to expect from the joint session of the House of Representatives and the Senate.

Both chambers of Congress are meeting to formally tally the Electoral College results, the final step in the months-long process to select the U.S. president. Vice-President Mike Pence will formally preside over the session.

The results are based on votes cast on Dec. 14 by slates of "electors" who met in each state to reflect the winner of that state's popular vote. A total of 538 electoral votes are allotted to states and the District of Columbia based on their congressional representation. Biden captured 306 electoral votes to Trump's 232.

The proceedings, which will kick off at 1 p.m. ET (18:00 GMT), are typically brief and ceremonial. This year, it could drag into Thursday, as some Republicans plan to challenge the result in key states.

Pence will open sealed certificates from the U.S. states and the District of Columbia that declare their electoral votes. Should Pence be unavailable, his duties can be carried out by the longest-serving senator in the majority party, Republican Senator Chuck Grassley of Iowa.

A bipartisan group of lawmakers will read the certificates out loud and officially tally the votes.

Objections to a state's results must be made in writing and endorsed by at least one Senator and one member of House of Representative.

If this happens, the joint session disbands and each chamber will hold a two-hour debate and vote on each objection one after the other. A majority of each chamber must support an objection for any electoral votes to be voided.

Republicans have suggested they will submit objections in writing to the results of as many as six battleground states.

Could Congress void Biden's win?

If enough electoral votes were voided, neither Biden nor Trump would have the 270 votes needed to secure the presidency, and Congress would pick the next president.

But there is virtually no chance of that happening.

A majority of both chambers needs to support an objection for electoral votes to be voided, and Democrats control the House.

Even the Senate, controlled by Republicans, is highly unlikely to vote to void votes.

Senator Ted Cruz and at least 11 other Republican senators are expected to reject electors. But most of the chamber's 100 members, including high-profile Republicans, have recognized Biden as the incoming president.

Senate Majority Leader Mitch McConnell, the body's top Republican, acknowledged Biden’s victory on Dec. 15 and has urged other Republicans to refrain from objecting on Wednesday.

Can Pence award the election to Trump?

No. Pence's role is ceremonial, and he doesn't have the power to overturn the results of the election despite being under pressure from Trump to do so.

Marc Short, Pence's chief of staff, said on Monday that while the vice president welcomed lawmakers' authority to raise objections and "bring forward evidence before the Congress and the American people," he will not deviate from his role.

"He ... will uphold the Constitution and follow the statutory law," Short told Reuters on Monday.

In the extremely unlikely event that Pence voids electoral college votes, his actions would almost certainly be challenged in court.