Barely two hours after Bernie Sanders emerged from a meeting with Barack Obama — saying he would keep campaigning ahead of the Washington, D.C. primary vote — President Obama endorsed his opponent in that primary, Hillary Clinton.

The Vermont senator warned that Trump would be a “disaster,” and echoed his promise Tuesday night in Santa Monica, California — which he had repeated many times during the Democratic primary race — that he would “work as hard as I can to make sure that Donald Trump does not become president of the Untied States.”

Speaking to reporters after an Oval Office meeting that lasted more than an hour, Sanders signaled an eventual reconciliation with the party’s likely nominee. “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,” he said.

Then the Clinton campaign released a video endorsement, marking the start of his active involvement in the campaign to replace him.

Hillary Clinton posted an announcement of the endorsement, with the president’s video, on Twitter, and followed up with her own message:

Honored to have you with me, @POTUS. I’m fired up and ready to go! -H

— Hillary Clinton (@HillaryClinton) June 9, 2016

Watch the president’s endorsement below:

Photo: U.S. President Barack Obama delivers remarks to reporters after meeting with India’s Prime Minister Narendra Modi in the Oval Office at the White House in Washington, U.S. June 7, 2016.  REUTERS/Jonathan Ernst