NEW YORK — Lisa P. Jackson has announced plans to step down as administrator of the U.S. Environmental Protection Agency following President Obama’s State of the Union address in January.

Jackson, who assumed the post four years ago, said in a statement that she leaves the EPA "confident the ship is sailing in the right direction."

The EPA has not yet named a replacement for Jackson, who said she is leaving to pursue "new challenges, time with my family and new opportunities to make a difference."