US Labor Secretary Hilda Solis resigned on Wednesday, becoming the latest member of President Barack Obama's cabinet to decide not to stay on in his second term.

Obama praised the Hispanic former lawmaker as a "tireless champion for working families" and said she had been a critical member of his team in helping the economy recover from the worst recession since the 1930s.

"Her efforts have helped train workers for the jobs of the future, protect workers' health and safety and put millions of Americans back to work," Obama said in a statement.

Solis had been among the cabinet secretaries that had been expected to depart Obama's cabinet as he freshens his team for a second term in which a priority is lowering the still high unemployment rate of 7.8 percent.

Obama will be under pressure to find women to replace Solis and other cabinet officers who are expected to leave, after naming Chuck Hagel and John Kerry to serve as secretaries of defense and state.

The president is also expected Thursday to name his White House chief of staff, Jack Lew, to be his next Treasury Secretary to succeed Timothy Geithner, sparking some complaints that his inner circle was insufficiently diverse.