New York City mayor Bill de Blasio will announce his candidacy for US president, a campaign spokeswoman has confirmed.
The 57-year-old mayor, who is barred from seeking a third four-year term in 2021, will add his name to a growing list of Democrats eager to take on Donald Trump in 2020.
Mr De Blasio will release a video announcing his run before appearing on ABC’s Good Morning America.
He is scheduled to travel to the early-voting states of Iowa and South Carolina this weekend to begin campaigning.
The mayor emerged in 2013 as a leading voice for the burgeoning left wing that has reshaped his party. But he has struggled in the intervening years to build a national profile, and his approval ratings at home have waned after several political setbacks.
Mr De Blasio faces an uphill struggle to stand out among nearly two dozen Democratic contenders, who include former US vice president Joe Biden and liberal icons such as US senators Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts.
The mayor has sharply criticised Mr Trump on issues such as climate change, immigration and policing.
On Monday, he held a news conference inside Trump Tower to call on the Trump Organisation to meet newly enacted emissions standards in their skyscrapers, or face significant fines.
In a preview of what could be to come, the event drew scathing insults on Twitter from Mr Trump’s two oldest sons, Eric and Donald Jr, who run the family company. The president retweeted a message from Eric Trump slamming Mr de Blasio’s stewardship of his family’s hometown.
Most New Yorkers appear unenthused about de Blasio’s presidential aspirations. A Quinnipiac University poll in April found more than three-quarters of New Yorkers did not feel he should make a White House bid.