San Antonio Mayor Julian Castro will be nominated as secretary of Housing and Urban Development, two officials told ABC News.

The White House declined to comment on the timing of an official announcement. The position must be confirmed by the Senate. The officials said the news was not intended to be disclosed, but apparently it leaked out because Castro's associates in San Antonio received calls from the FBI about a background check. It was first reported in a column in today's San Antonio Express News.

Read more: ABC Asks Hillary Clinton About Warren, Casto as Possible VP Picks

Current HUD Secretary Shaun Donovan will likely be tapped to lead the Office of Management and Budget as part of a restructuring in the Cabinet after Kathleen Sebelius stepped down as secretary of Health and Human Services last month.

WATCH: Julian Castro: We'll See a Latino U.S. President In Our Lifetime

The 39-year-old Castro is a rising star in the Democratic Party. He delivered the keynote address at the party's 2012 convention in Charlotte, N.C. His twin brother, Joaquin, is a Democratic congressman from Texas.

Read more: Meet Julian Castro

If Castro is indeed nominated and confirmed, he will instantly add political star power to the president's Cabinet. He has been speculated to be a possible Democratic vice presidential pick in 2016, and ABC's Robin Roberts asked Hillary Clinton about the possibility of running with Castro, should she enter the presidential race and win the Democratic primary.

Read more: The Blue Brothers: Castro twins predict that Texas won't be a red state for long

"Were you to run for president in 2016, would you consider Elizabeth Warren or Julian Castro for your running mate?" ABC's Roberts asked Clinton earlier this month, at an event in New York.

Clinton called both of them "extraordinary leaders."

In a January video interview with ABC/Yahoo!, Castro said he'll support Clinton if she runs. Julian and his brother Joaquin said they think Texas is on its way to electing more Democrats than Republicans.

Introduced to politics by his mother, who was part of a movement in Texas that pushed for civil rights for Mexican-Americans, Castro and his brother both attended Stanford and then Harvard Law School. At 26, he became the youngest-ever member of San Antonio's city council. He was elected mayor in 2009 and won reelection in 2011 with 80 percent of the vote.

Calls to Castro's office and campaign weren't immediately returned.