Washington: Former Maryland governor Martin O'Malley on Saturday announced his bid for the 2016 US presidential race, in which he will first face tough challenge from former secretary of state Hillary Clinton to win the Democratic nomination.

"I declare that I am a candidate for president of the US," O'Malley told a crowd of supporters at the Federal Hill Park in Baltimore, where he served as mayor before becoming Maryland's governor for 2007-2015, Xinhua reported.

"My decision is made. Now you will all have a vital choice to make next year, for the good of your families, and for the good of the country you love and carry in your hearts," he said.

O'Malley, 52, joined Vermont Senator Bernie Sanders and Hillary Clinton in the Democratic field to compete for the party nomination next year.

Clinton is being regarded as the frontrunner, but O'Malley said Democrats deserve a choice in the 2016 primary.

In a veiled attack at Clinton, O'Malley said the US presidency "is not a crown to be passed back and forth … between two royal families", referring to the Clinton and Bush families.

Hillary Clinton's husband Bill Clinton occupied the White House for two terms during 1993-2001.

Former Florida governor Jeb Bush, brother of former president George W. Bush (2001-2009) and son of former president George H.W. Bush (1989-1993), is expected to soon announce his bid for the 2016 Republican nomination.

Jeb Bush is regarded as the top contender among an already crowded Republican field, which currently includes eight candidates after former New York governor George Pataki announced on Thursday his run for the 2016 race. (IANS)