Tulsi Gabbard and Julian Castro announce campaigns for 2020 presidential election

Tulsi Gabbard, the first Hindu elected to Congress, and Julian Castro, the former San Antonio mayor, have announced campaigns to run for the presidency in 2020 as the Democrat challenger to President Donald Trump.

Mrs Gabbard, 37, is a congresswoman from Hawaii while Mr Castro, 44, served as housing and urban development secretary during Barack Obama's presidency. 

They will both face fierce competition to win the Democratic Party’s nomination given politicians with higher profiles are expected to join the race soon. 

Mrs Gabbard, a veteran of the Iraq war who backed Bernie Sanders for the Democratic nomination over Hillary Clinton in 2016, announced her plans on Friday.

She recently made stops in both Iowa and New Hampshire – vital early voting states - and looked into hiring digital staff and speechwriters. She has also authored a memoir, which is set to be released in May.

“I have decided to run and will be making a formal announcement within the next week,” she said during an interview on CNN.

Mr Castro, the grandson of a Mexican immigrant who would be the first Hispanic elected president, revealed his presidential hopes on Saturday.

"I'm running for president because it's time for new leadership. Because it's time for new energy," he said, launching his campaign. "And it's time for a new commitment to make sure that the opportunities I've had are available for every American."

Mr Castro has sought to use his family's personal story to criticize Mr Trump's border policies - including criticising the president by name in his launch speech.

"Yes, we must have border security, but there is a smart and humane way to do it. And there is no way in hell that caging children is keeping us safe," Mr Castro said.

Mrs Gabbard's run would not be without controversy. In 2016, she alarmed fellow Democrats when she met with Donald Trump during his transition to president and later when she took a secret trip to Syria and met with President Bashar Assad, who has been accused of war crimes and genocide.

She questioned whether he was responsible for a chemical attack on civilians that killed dozens and led the US to attack a Syrian air base.

She said she doesn't regret the trip and considers it important to meet with adversaries if "you are serious about pursuing peace." She also noted that the 2003 invasion of Iraq was based on faulty intelligence and said that she wanted to understand the evidence of the Syria attack.

Mrs Gabbard was one of the most prominent Democrats to back Mr Sanders over Hillary Clinton in the 2016 Democratic presidential primary. Her endorsement came in dramatic fashion, with her resigning as a vice chairwoman of the Democratic National Committee to express her support.

Asked last year whether she would still consider running if Sanders ran, Mrs Gabbard said Mr Sanders is a friend and she didn't know what his plans were.

"I'm thinking through how I can best be of service and I'll make my decision based on that," she said. 

Both politicians' entrance into a growing Democrat presidential primary field comes before an expected wave of similar announcements from higher profile candidates.

Elizabeth Warren, senator for Massachusetts, has already announced that she is intending to run, and Kamala Harris, senator for California, is also thought likely to declare her intention in the coming weeks.

Joe Biden, the former vice president, insists he is undecided yet many expect him to throw his hat into the ring.