Democratic presidential candidate Bernie Sanders suspended his campaign on Wednesday, making former Vice President Joe Biden the presumptive nominee to face Republican President Donald Trump in the Nov. 3 election.

Sanders, a democratic socialist who had promised to lead a grassroots political revolution into the White House, acknowledged he no longer had a viable path to the nomination and promised to work with Biden to take on Trump.

But he said he would stay on the ballot in future primaries and continue to gather delegates in order to push the Democratic platform toward his populist anti-corporate agenda, including a government-run healthcare system and tax hikes for the rich.

"Then together, standing united, we will go forward to defeat Donald Trump, the most dangerous president in modern American history," he said in a livestreamed speech to supporters from his hometown of Burlington, Vermont.

The 78-year-old U.S. senator from Vermont, whose progressive agenda pulled the party sharply to the left, was an early front-runner in the Democratic race before losing in South Carolina in late February as moderate Democrats united behind Biden. The departure of Sanders, the last remaining rival to Biden, sets up a long race for the White House between the 77-year-old former vice president and Trump, 73, who is seeking a second four-year term in office.