White House hopeful Joe Biden spent the last year clashing over policy with Bernie Sanders, but on Tuesday the frontrunner openly courted his leftist rival's young voters, telling them: "I hear you."

After scoring decisive primary victories in Florida and Illinois that saw Biden march closer to the Democratic presidential nomination, the former vice president said it was time to unite the party's factions in order to defeat Republican incumbent Donald Trump in November.

Biden, 77, praised Sanders and his followers for having "shifted the fundamental conversation in this country" during the yearlong campaign.

"Let me say especially to the young voters who have been inspired by Senator Sanders: I hear you, I know what's at stake," he said in televised remarks after polls closed in the two states.

"My goal as a candidate for president is to unify this party and then to unify the nation."

Biden, who was speaking before he notched up his third primary victory of the night, in Arizona, claimed that he and the 78-year-old Sanders were aligned on several key policies.

Former US vice president Joe Biden, who leads the Democratic presidential nomination race, has appealed to supporters of his rival Bernie Sanders, saying it is time to unite the party and the country to defeat President Donald Trump in November 2020
Former US vice president Joe Biden, who leads the Democratic presidential nomination race, has appealed to supporters of his rival Bernie Sanders, saying it is time to unite the party and the country to defeat President Donald Trump in November 2020 AFP / SAUL LOEB

"Senator Sanders and I may disagree on tactics but we share a common vision" for expanding affordable health care, reducing economic inequality and tackling climate change, Biden said.

Sanders spokeswoman Briahna Joy Gray had a two-word retort to Biden's claim of sharing a common vision: "We don't," she tweeted.

The pushback suggests that despite Biden's flattery of Sanders voters, there may be difficulty ahead in winning over liberal followers who see Biden as the embodiment of establishment politics.

Sanders has long called for a political revolution. Biden has scoffed at the rhetoric and repeatedly stressed that the best way to expand health coverage is to build on the existing Obamacare, not upend the economy with Sanders's plan to shift to a government run health care system.

At their Sunday debate, Sanders expressed "doubts" that Biden could generate enough enthusiasm and voter turnout among Latino and young voters to defeat Trump in November.

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