WASHINGTON - US Energy Secretary Steven Chu on Friday announced his intention to resign to  end a four-year tenure with the Obama administration.

Chu made the announcement in a letter to department employees, saying he intends to resign once a successor is confirmed.

"While I will always remain dedicated to the missions of the department, I informed the president of my decision a few days after the election that Jean and I were eager to return to California," Chu wrote in the lengthy letter. "I would like to return to an academic life of teaching and research but will still work to advance the missions that we have been working on together for the last four years."

But in the short term, Chu said he plans to stay on past the end of February, and may stay on longer in order to "leave the department in the hands of the new secretary."

President Barack Obama has not yet announced Chu's successor, but reports speculated former North Dakota Sen. Byron Dorgan, former Colorado Gov. Bill Ritter, former Washington Gov. Chris Gregoire and former Michigan Gov. Jennifer Granholm could be on the short list.