US Republican Donald Trump says Democratic front-runner Hillary Clinton is only doing well in the election because of her gender.
"Frankly, if Hillary Clinton were a man, I don't think she'd get five per cent of the vote," Trump told reporters on Tuesday.
"The only thing she's got going is the woman's card. And the beautiful things is, women don't like her, okay?"
Trump was speaking in Manhattan after sweeping primaries in all five states that voted on Tuesday.
Both he and Clinton have high unfavourable ratings, and Trump has made clear that he intends to attack the woman he calls "crooked Hillary" mercilessly if the pair wind up facing off in a general election.
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Trump also suggested twice that Clinton's rival, Bernie Sanders, run as an independent.
Clinton, in a victory speech in Philadelphia on Tuesday night, took aim at Trump for accusing her of trying to play the woman card in seeking to become the first female US president.
"Well if fighting for women's healthcare and paid family leave and equal pay is playing the woman card, then deal me in," she told her supporters.
