Sanders spoke in a livestream address to political supporters, two days after the final primary election of the nomination race.
The major task they now faced was to “make certain” the presumptive Republican nominee lost in November, he said, adding that he planned to begin his role in that process “in a very short period of time.”
“But defeating Donald Trump cannot be our only goal”, Sanders said, pointing to his 1,900 delegates for next month’s Democratic national convention in Philadelphia.
“We must continue our grassroots efforts to create the America that we know we can become.”
His campaign manager Jeff Weaver said a “tremendous burden” was falling on Clinton to demonstrate she had heard the voices of the young people who powered his effort.
Weaver said the Sanders team was in contact with the Clinton campaign daily.
Yet, when asked, on MSNBC, whether Sanders was still running for president, Weaver said: “Yes he is.”
Although Clinton has enough pledged delegates and superdelegates to become the presumptive nominee, Sanders has not conceded the race.