President Barack Obama took the first major step to unify the Democratic Party on Thursday, meeting with Senator Bernie Sanders in the Oval Office and issuing a video endorsement of Hillary Clinton right afterwards.

“I don’t think there’s ever been someone so qualified to hold this office,” Obama says in a video released by the Clinton campaign. “She’s got the courage, the compassion, and the heart to get the job done. I have seen her judgment. I’ve seen her toughness. I’ve seen her commitment to our values up close. And I’ve seen her determination to give every American a fair shot at opportunity, no matter how tough the fight — that’s what’s always driven her, and still does.”

Earlier Thursday, Obama met with Sanders in the Oval Office. Following the hour-long meeting, Sanders pledged to “work as hard as I can to make sure” that Donald Trump does not become president. “I look forward to meeting with (Clinton) in the near future to see how we can work together to defeat Donald Trump and to create a government which represents all of us and not just the 1 percent,” Sanders told reporters outside the White House.

Obama is expected to join the campaign trail, holding a joint rally with Clinton in Green Bay, Wisconsin next Wednesday.

“Obama just endorsed Crooked Hillary. He wants four more years of Obama—but nobody else does!” preemptive Republican presidential nominee Donald Trump tweeted minutes after the endorsement was made public.

“Delete your account,” Clinton tweeted in response.

Obama just endorsed Crooked Hillary. He wants four more years of Obama—but nobody else does!

— Donald J. Trump (@realDonaldTrump) June 9, 2016

Delete your account. https://t.co/Oa92sncRQY

— Hillary Clinton (@HillaryClinton) June 9, 2016