Story highlights U.S. Labor Secretary Tom Perez will endorse Hillary Clinton in Iowa on Friday

Perez is the third member of President Barack Obama's cabinet to endorse Clinton

Manchester, New Hampshire (CNN) U.S. Labor Secretary Tom Perez will formally endorse Hillary Clinton in Iowa on Friday, according to a campaign aide, joining the presidential candidate for two campaign events in the Hawkeye State.

The endorsement likely stings for former Maryland Gov. Martin O'Malley, Clinton's Democratic opponent, who helped launch Perez's career when he appointed him to serve as secretary of the Maryland Department of Labor, Licensing and Regulation in 2007.

Perez said that he was standing behind Clinton because she 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."

"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," he said in a statement provided by the Clinton campaign.