Trump, speaking at the Ellipse, just outside the White House grounds, before thousands of supporters Wednesday, repeated he will "never concede" -- and ramped up pressure on Vice President Mike Pence to try to overturn the outcome at a joint session of Congress just minutes away -- which Pence cannot do.

"We will never give up. We will never concede," Trump said from behind plexiglass to chants of "Fight for Trump."

"All Vice President Pence has to do is send it back to the states to re-certify, and we become president, and you are the happiest people," Trump said, teasing the 1 p.m. joint session of Congress to formally count the Electoral College votes.

"And Mike Pence is going to have to come through for us, and if he doesn't, that will be a sad day for our country," Trump added.

Trump said he would lead the crowd of supporters to the Capitol Building following his remarks.

"And we’re going to cheer on our brave senators and congressmen and women. And we’re probably not going to be cheering so much for some of them. Because you’ll never take back our country with weakness," he said.

"We’re going to see whether or not we have great and courageous leaders, or whether or not we have leaders that should be ashamed of themselves throughout history -- throughout eternity. They’ll be ashamed. And you know what? If they do the wrong thing, we should never, ever forget that they did. Never forget. We should never, ever forget," Trump said.

"We got to remember, in a year from now, you're going to start working on Congress, and we've got to get rid of the weak congresspeople. The ones that aren't any good. The Liz Cheneys of the world," he went on.

"Mike Pence, I hope you're going to stand up for the good of our Constitution and for the good of our country. And if you're not, I'm going to be very disappointed in you."

As Congress convenes for a joint session Wednesday to ratify the Electoral College vote confirming Biden’s win, a historic showdown looms large as a handful of Republican lawmakers have said they will challenge Biden’s win.

More than 100 GOP lawmakers in the House and at least a dozen in the Senate are expected to join with President Trump in a last-ditch effort to challenge his election loss.

Democrats are calling this an unprecedented attack on American democracy, upending what is traditionally a solemn and relatively routine process of counting the certified electoral votes from each states.

The Republican lawmakers’ complaints, however, are not expected to shift the final outcome.

The joint session convenes at 1 p.m. ET.

-ABC News’ Benjamin Siegel

Sen. Josh Hawley, R-Mo., one of the 13 Republicans who plan to launch objections to the electoral ratification Wednesday afternoon, said on Fox during an interview with Laura Ingram Tuesday night that he does not believe Vice President Pence has the ability to not accept the electoral vote count.

Pence does not have the ability to overturn the election, despite tweets to the contrary from the president.

"I don't think the Vice President counts under the law," Hawley said. "I mean, he's sort of just there."

Hawley is a close ally of Trump but broke with the president on this issue.

"This is really on Congress," Hawley said. "This is why it's important to object and why I intend to object."

-ABC News’ Allie Pecorin

In his first tweet of the morning, President Donald Trump continued Wednesday to pressure Vice President Mike Pence to overturn the election -- which Pence cannot do.

Trump continued to peddle his false claims of election fraud, telling Pence, "Do it Mike, this is a time for extreme courage!"

Meanwhile, the nation’s capital is bracing for protests as Trump supporters convene for a rally in Washington, D.C.

Trump is expected to speak at 11 a.m. at what’s being called a “Save America Rally” from the Ellipse park just beside the White House.

Also Wednesday, a showdown looms in Congress as a handful of Republican lawmakers prepare to challenge Biden’s win.

-ABC News' Elizabeth Thomas