Democratic senator Elizabeth Warren moves toward 2020 U.S. presidential bid

Democratic Senator Elizabeth Warren announced on Monday that she has formed an exploratory committee, a major move toward a 2020 presidential run.

In a four-and-a-half minute video, Warren of the U.S. state of Massachusetts touched upon topics likely to define her upcoming campaign, such as economic equality, government accountability and reining in big corporations.

"Every person in America should be able to work hard, play by the same set of rules, and take care of themselves and the people they love," Warren said in the video.

"That's the America I'm fighting for. And that's why today I'm launching an exploratory committee for president," she added.

Warren, 69, has represented Massachusetts in the Senate since 2013. In November, the Democrat won re-election to the upper chamber for a second term.

She is believed to be the most prominent Democrat yet to take formal action toward a presidential bid.

In an email to supporters, Warren said she would more formally announce a campaign plan early in 2019.

U.S. President Donald Trump has frequently mocked Warren's claim that she has Native American heritage.