Updated 11:20 a.m. ET
WASHINGTON Environmental Protection Agency Administration Lisa Jackson says she's stepping down after nearly four years on the job.
Jackson announced her departure in a statement Thursday. She gave no particular reason for leaving but said she was ready for new challenges, time with her family and new opportunities to make a difference.
Jackson's tenure was marked by high-profile brawls with industry and congressional Republicans over such issues a global warming pollution, the Keystone XL oil pipeline and new controls on coal-fired plants.
She says she's leaving the agency, in her words, "confident the ship is sailing in the right direction."
In a written statement, President Obama said, "Under her leadership, the EPA has taken sensible and important steps to protect the air we breathe and the water we drink, including implementing the first national standard for harmful mercury pollution, taking important action to combat climate change under the Clean Air Act, and playing a key role in establishing historic fuel economy standards that will save the average American family thousands of dollars at the pump, while also slashing carbon pollution."
Jackson is expected to leave after the State of the Union address in late January. Cabinet members looking to move on often leave at the beginning of a president's second term.