Bernie Sanders laughed out loud when he was asked if he was “sexist” for staying in the presidential race as he was making it harder for the US to elect its first woman president.

“Is that a serious question?” he asked the female reporter.

“Yes it is a serious question,” she replied.

“Your question implies that any woman, that any person, any woman who is running for president is by definition the best candidate,” he said.

“So if Hillary Clinton runs for president, is your point that it is sexist for any man to oppose?”

The reporter responded that her point was that Ms Clinton has more delegates and super delegates than Mr Sanders and is therefore more likely to win the nomination.

Mr Sanders said the issue of delegate maths was a separate issue.

“I don’t think it is sexist," he said. "[...] our focus right now is running and winning right here in California and the second point that I have made is that it is absolutely imperative that we defeat Donald Trump as a candidate for president of the United States. I believe that I am the stronger candidate.”

Mr Sanders and his supporters called out the media over the weekend for "bias" against him and for calling Ms Clinton the Democrat nominee before the super delegates have even voted at the Democratic convention.

His comments on sexism come the day before the primary in California, which is crucial for Mr Sanders to gain more delegates and to stop Ms Clinton from securing the party nomination.

Ms Clinton has previously criticized Mr Sanders for his comments on abortion. He claimed his comment that the media should focus on “the real issues” was taken out of context, as he was referring to reporters' fixation on Mr Trump's remarks on the subject.