Former President Barack Obama will endorse his former vice president Joe Biden in a video to be released Tuesday, according to a source close to the former president.

The endorsement will come one day after Sen. Bernie Sanders, I-Vt., offered Biden his endorsement during a livestream. Sanders ended his campaign for president last week, leaving Biden as the apparent nominee.

Obama had publicly remained on the sidelines as the primary played out, though he offered advice to candidates behind the scenes. In recent weeks he had several calls with Sanders to try and figure out the best path forward for Democrats, a source close to the former president told NBC News last week.

By remaining out of the public spotlight, Obama hoped to help unify the party once the primary had wrapped.

In recent weeks, Obama has ramped up his presence on social media, posting mostly about information on the COVID-19 outbreak that he believes should be widely shared.

Last week, President Donald Trump questioned why Obama had yet to endorse Biden.

“I’m sure he’s got to come out at some point because he certainly doesn’t want to see me for four more years,” Trump said, adding, “When is it going to happen? When is it going to happen? Why isn’t he?”

When Biden announced his candidacy, he was soon after asked why Obama hadn’t already endorsed him.

“I asked President Obama not to endorse,” he told reporters. “Whoever wins this nomination should win the nomination on their own merits.”

Obama’s involvement at the end of the race mirrors what was seen in 2016. Once former Secretary of State Hillary Clinton clinched the nomination in June, Obama met with Sanders at the White House before making his endorsement of Clinton public. Sanders then waited another month before endorsing Clinton himself. This time, however, Sanders announced his endorsement of Biden prior to Obama’s rollout.

While Obama remained on the sidelines, Biden has all but bear-hugged the former president in his comments on the campaign trail, as Obama remains highly popular with Democrats.

“If you notice, every major historian has written about the presidency and the vice presidency, and they’ve said of late, that no vice president or president has ever been closer than Barack Obama and Joe Biden in American history,” he told voters in Iowa in January. “That’s been the consensus. And there’s a reason for that, because we both trusted each other, completely. And we knew, and he knew from the beginning, I would never, ever, ever do anything, that was inconsistent with his interest.”