Senator Bernie Sanders exhorted his millions of supporters to fight to implement progressive policies to transform America, saying the general election was more than about beating Donald Trump.

In a speech lasting more than an hour, the 74-year-old from Vermont, who challenged Hillary Clinton for the Democratic nomination from the left, failed to mention the victorious secretary of state even once.

Instead, he insisted that the popularity of his campaign, particularly among people under 45, proved the establishment could be beaten and urged his supporters to continue the fight for radical change.

"We have got to work tirelessly to make sure that Trump is not president. But that is not good enough," he said in New York less than six months before Americans vote for a new president in November.

"What we have got to do is to continue the vision of transforming this country. And the most important way I know we can do that, is for all of us to get involved in the political process," Sanders said.

Trump has inflamed large swathes of America by running a divisive campaign that has insulted ethnic minorities, called Mexicans rapists, demanded a ban on Muslims entering the country and denigrating women.

"The cornerstone of his campaign is bigotry," said Sanders, vowing to do "everything I can" to defeat Trump, even "if I have to run all over this country to do it."

Sanders said the Democrats' platform for the election would be its most progressive in history, but warned promises on paper counted for nothing if they were not enacted.

"That platform doesn't mean anything unless we make certain those ideas are incorporated into public policy," he said.

The platform would oppose trade deals, fight to ban the sale and distribution of assault weapons and expand background checks on those buying weapons, he said.

His speech was a battle cry for his followers to continue to campaign for change from the ground up, stretching from school boards, to city councils, state elections and federal politics.

"I have no doubt that a strong, well-organized grass-roots movement can... defeat the establishment and that is precisely what we have got to do and what the political revolution is about," he said.

Clinton for all intents and purposes won their at-times bitter battle for the Democratic nomination earlier this month by clinching the number of delegates needed to become the party flag bearer.

Source: AFP