US Democratic presidential candidate Bernie Sanders says the Democratic Party establishment has not been fair to him and has favored his main rival Hillary Clinton.

"Do you think this process has been fair to you? The Democratic nomination process?" moderator Chuck Todd asked the Vermont senator in an interview filmed Saturday in Baltimore and aired Sunday on NBC's "Meet the Press."

"No," Sanders responded. "I think we have— look, we're taking on the establishment. That's pretty clear."

"But you know, that's the way it is. We knew we were taking on the establishment," he said. "And here we are.”

Todd then asked Sanders if he felt he was "given a fair shot" at the Democratic nomination.

"Yeah, we took advantage of the opportunities in front of us. We are in this race. We are not writing our obituary," Sanders said. "We're in this race to California, and we're proud of the campaign we ran."

While acknowledging that his path to victory is "narrow," Sanders said he could do "very well in California," pointing to recent poll showing him down in the state by just two percentage points.

He also pointed to polls showing him faring better than Clinton against Republican presidential frontrunner Donald Trump in a hypothetical general-election contest.

Sanders suggested that he would not necessarily push his supporters to back Clinton if he is not the Democratic nominee.

"I will do everything that I can to make certain that Donald Trump is not elected president, but if that scenario plays out, the major responsibility will be on Secretary Clinton to convince all people, not just supporters, that she is the kind of president this country needs to represent working people in this country, to take on the big money interests who have so much power, to fight for what the American people want."