Julian Castro and Tulsi Gabbard have both announced plans to join what's set to be a crowded field of candidates
Two more Democrats in the US have announced their plans for 2020 presidential bids.
Julian Castro and Tulsi Gabbard join Senator Elizabeth Warren and former Congressman John Delaney in what's set to grow into a crowded field of presidential hopefuls.
Mr Castro served as housing secretary during the final years of Barack Obama's administration.
The 44-year-old was also reported to be a potential vice-presidential running mate for Hillary Clinton (a role which ultimately went to Senator Tim Kaine), and served as mayor of the Texas city of San Antonio from 2009 to 2014.
Announcing his presidential bid, Mr Castro wrote: "I’ve spent my life in public service, giving back to this country everything it’s given to me.
"I want to ensure that America’s future is one where every person gets the chance they deserve and the opportunity they need to thrive."
Tulsi Gabbard, meanwhile, confirmed her plans in an interview with CNN ahead of a formal launch in the coming week.
The Hawaii Congresswoman told the network: "There are a lot of reasons for me to make this decision. There are a lot of challenges that are facing the American people that I'm concerned about and that I want to help solve.
"There is one main issue that is central to the rest, and that is the issue of war and peace."
Mrs Gabbard - the first Hindu to serve in the House of Representatives - has served in Congress since 2013, and was overwhelmingly re-elected last year.
While considered a progressive on several key issues, she's also faced some high-profile criticism during her time in office - in particular over a 2017 meeting with Syrian leader Bashar al-Assad.
So far, Senator Warren remains the most prominent Democrat to have publicly expressed plans for a presidential bid.
However, several other prominent figures in the party - including senators Kamala Harris, Cory Booker and Kirsten Gillibrand - are widely expected to announce their own intentions in the coming weeks and months.
Other possible candidates include former vice president Joe Biden and independent senator Bernie Sanders.
With the chosen candidate expected to run against Donald Trump, the Democrats' own primary race is set to be a battle between the party's traditional, 'establishment' wing and a burgeoning progressive movement.
The race is getting underway with more than a year still to go until the first major primary vote in Iowa.