Julián Castro, the former mayor of San Antonio and secretary of Housing and Urban Development under President Obama, says he has "every interest in running" for president in 2020.

Castro is expected to headline the New Hampshire Young Democrats Granite Slate Awards Dinner next Friday - a move that could mark the start of a 2020 bid. New Hampshire, which holds the country's first presidential primaries, is usually a strong testing ground for candidates eyeing a presidential run.

"I have every interest in running" for president, Castro told NBC News. "Part of the process of figuring out whether I'm going to run is going to listen to folks and feel the temperature of voters."

The event hosted by the Young Democrats is usually attended by a little more than 100 people. This year, however, interest has been so high they had to move the event to a larger venue. Tickets are selling for $30 to $2,500.

Castro, who was considered as a possible running mate for Hillary Clinton's 2016 presidential campaign, has not been shy about his political ambitions.

He first got into politics in 2001 when he was elected to the San Antonio City Council as a 26-year-old and formed his own political action committee last year, stirring speculation of a run.

Since his tenure with the Obama administration ended, Castro has returned to writing a memoir he put on hold when he became HUD secretary that is set to be published in 2018. He currently is teaching at the Lyndon B. Johnson School of Public Affairs at the University of Texas.