Labor Secretary Thomas E. Perez, who has become one of President Obama's top emissaries to liberal, labor and Latino constituencies, is backing Hillary Clinton for president and plans to hit the campaign trail on her behalf.

Perez, who plans to formally endorse Clinton on Friday in Iowa, portrayed Clinton as a progressive fighter who can grab the baton from Obama and take care of the nation's "unfinished business."

"Progressives believe in making progress, which is why I'm proud to endorse Hillary Clinton who I know will continue fighting to ensure our children and grandchildren can achieve their highest and best dreams," Perez said in a statement provided by the Clinton campaign. "Secretary Clinton is tough, smart, and understands better than any candidate the challenges that parents are talking about around dinner tables and keeping families up at night."

Perez added, "In the coming months, I look forward to hitting the campaign trail to highlight the progress we've made as a nation, the unfinished business, and why Hillary Clinton is the fighter we need leading that effort."

Perez's endorsement is significant for Clinton considering his ties to one of her rivals for the Democratic nomination, former Maryland governor Martin O'Malley. Perez, who lives in Takoma Park and once was a member of the Montgomery County Council, served in O'Malley's cabinet as the state's secretary of labor, licensing and regulation.

During Obama's first term, Perez served at the Justice Department as assistant attorney general for the civil rights division and was deeply immersed in police discrimination and voting rights issues. In 2013, Obama promoted him to secretary of labor.

A son of Dominican immigrants, Perez has strong relationships with key leaders and activists in the liberal, labor and Latino communities, which are influential in Democratic primary politics. Should Clinton be elected president, Perez would be a likely contender to serve in her Cabinet, perhaps as attorney general.

Perez is the third Obama Cabinet member to endorse Clinton, joining Thomas J. Vilsack, the secretary of agriculture and a former governor of Iowa, and Julián Castro, the secretary of housing and urban development and a former mayor of San Antonio.

A Clinton campaign official said Perez intends to campaign vigorously as a Clinton surrogate, including trips to early voting states and places with large Latino populations.

Perez's endorsement comes after Clinton has received the endorsements of 15 national labor unions representing more than 11 million workers.