WASHINGTON - A US senator from the state of New York on Sunday formally announced her bid to become the next US president, joining a crowded group of candidates jockeying for the Democratic nomination.

"I'm running for president. Let's prove that brave wins," Kirsten Gillibrand made the announcement on Twitter with a 2.5-minute campaign video titled "The Brave".

"We need to remember what it feels like to be brave. Brave doesn't pit people against each other or put money over lives. It doesn't spread hate, cloud truth or build a wall. That's what fear does," she said.

Gillibrand plans to visit Michigan, Iowa and Nevada in the coming week for public appearances, before arriving back to New York City for her kickoff speech on March 24.

She has painted herself as a fierce Trump critic, and prided herself for voting against many of Trump's important political nominees. She has also been an advocate of women's rights, including anti-sexual misconduct and equal treatment for women.

Gillibrand, 52, is a New York native born to a political family. She practiced law before entering the House of Representatives in 2007. She was appointed to the Senate seat in 2009, after her predecessor Hillary Clinton was tapped to lead the State Department.

With more than a dozen candidates seeking the Democratic nomination, Gillibrand is currently lagging in the polls behind bigger names including US Senator from Vermont Bernie Sanders, Senator from California Kamala Harris and former member of Congress Beto O'Rourke.