"The numbers tell us ... it's a clear and convincing story," Biden said, adding that he and his running mate Kamala Harris were already meeting with experts as they prepare for the White House.
Biden's speech was originally planned as a victory celebration, but he changed his approach in the absence of an official call from television networks and other election forecasters.
Still, it amounted to a blunt challenge to Trump, who kept out of view in the White House on Friday as Biden's lead grew in the four states that will decide the outcome: Pennsylvania, Georgia, Arizona and Nevada.
Leading Trump by 4.1 million votes nationwide out of a record 147 million cast, Biden said Americans had given him a mandate to tackle the coronavirus pandemic, the struggling economy, climate change and systemic racism.
JOE BIDEN: We don't have a final declaration of victory yet, but the numbers tell us it's clear-- tell us a clear and convincing story. We're going to win this race. I know watching these vote tallies on TV moves very slow, and as slow as it goes, it can be numbing. But never forget that tallies aren't just numbers. They represent votes and voters. Men and women who exercised their fundamental right to have their voice heard.
And what's becoming clearer each hours is that a record number of Americans of all races, faiths, religions chose change over more of the same. They've given us a mandate for action on COVID, the economy, climate change, systemic racism. They made it clear they want the country to come together, not continue to pull apart.
We have to remember the purpose of our politics isn't total unrelenting, unending warfare. No. The purpose of our politics, the work of the nation isn't to fan the flames of conflict, but to solve problems.
We're certainly not going to agree on a lot of issues, but at least we can agree to be civil with one another. We have to put the anger and the demonization behind us. It's time for us to come together as a nation to heal.
I hope to be talking to you tomorrow. I want to thank you all. And may God bless you, and may God protect our troops.