Joe Biden has chosen California Senator Kamala Harris as his Vice President candidate, making her the first black woman on a major party presidential ticket.
Senator Harris is a lawyer who has served in the US Senate since 2017.
US President Donald Trump has criticised his Democratic rival's vice presidential selection process and said some men are "insulted" by Joe Biden's pledge to pick a woman as his running mate.
In an interview with Fox Sports Radio, Mr Trump said: "I would be inclined to go a different route than what he's done."
He said Mr Biden had "roped himself off into, you know, a certain group of people".
Mr Biden is expected to announce his running mate in the coming days ahead of next week's Democratic National Convention.
The United States has never had a female vice president, and the move comes four years after Hillary Clinton, the country's first female presidential nominee, lost her White House bid.
Of Mr Biden's vow to choose a woman, Mr Trump said: "Some people would say that men are insulted by that. And some people would say it's fine."
Biden campaign spokesman Andrew Bates said Mr Trump is "easily threatened".
In a statement, Mr Bates said: "And because of his insulting negligence and erratic, failed leadership, over 5 million Americans have been infected with coronavirus, over 160,000 died, and tens of millions remain jobless."
Reporting by PA
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