Sanders, who has yet to officially suspend his Democratic presidential campaign, said he'll continue pressing for the policies that animated his failed presidential bid before the party's 2016 platform is locked in at the Democratic National Convention in Philadelphia next month.
"We lost some very important fights," Sanders told CNN's Jake Tapper on "State of the Union." "We're going to take that fight to Orlando, where the entire committee meets in two weeks. And if we don't succeed there, then we'll certainly take it to the floor of the Democratic convention."
Sanders' victories in the platform include a $15-an-hour minimum wage, efforts to curb "Wall Street greed" and hiking taxes on multi-millionaires. But it does not line up with Sanders' positions on trade, a carbon tax and a Medicare-for-all single-payer health insurance system.
"We have made some good gains," Sanders said. "We have more to do."
Sanders has said he'll support presumptive Democratic presidential nominee Hillary Clinton and do everything he can to defeat Republican Donald Trump in November. But, pressed about polls that show nearly half of his voters not currently supporting Clinton, Sanders said she'll need to embrace progressive policy positions to win over those supporters.
"And if she does the right thing, I am absolutely confident that the vast majority of my voters will vote for her," Sanders said.
"That is the process we are engaged in right now. We're working on the Democratic platform. We are talking to the Clinton campaign," he said. "And I hope very much that Secretary Clinton understands that not only is it good public policy, it's the right thing to do; it is good politics to begin to move in that direction."
Sanders said he doesn't believe Trump will win in the general election -- in part because of his refusal to accept climate science and his proposed cuts in taxes for the wealthy.
Sanders also said Trump goes against "centuries of struggle that we have had in this country to combat discrimination."
"That is not the candidate that the American people are going to support in November," he said.