UPDATE 2-U.S. Interior head Salazar to leave administration

* Led the government's response to BP oil spill

* Would be second of Obama's energy team to depart

* Known for signature bolo tie and cowboy hat

WASHINGTON, Jan 16 (Reuters) - U.S. Interior Secretary Ken Salazar, who helped lead the government's response to the largest offshore oil spill in U.S. history, will announce he is stepping down from his post, an Obama adminisration official said on Wednesday.

The former U.S. senator from Colorado came to office pledging to clean up the "mess" at the Interior Department, but it was the massive 2010 BP oil spill in the Gulf of Mexico that ultimately spurred the dramatic overhaul of the nation's offshore drilling regulator.

Salazar's departure comes as President Barack Obama's cabinet undergoes the typical make-over for his second term. Other energy officials, including Environmental Protection Agency head Lisa Jackson, have already announced they would not be staying on. Energy Secretary Steven Chu is also widely tipped to leave.

The Denver Post, which first reported Salazar's move, said President Barack Obama had wanted him to remain at the department, which has a key role in regulating industries such as energy and mining on public lands.

A successor to Salazar at the Interior Department, which manages hundreds of millions acres including national parks and national forests, will likely come from a western state, where most federally-owned lands are located.

Potential candidates for the Interior post include outgoing Washington Governor Christine Gregoire, former Senator Jeff Bingaman, who was chair of the Senate energy committee, and Bill Ritter, former governor of Colorado.

Salazar is expected to leave the administration by the end of March to return to his Colorado ranch, according to media reports.

Raised on his family's ranch in Colorado, Salazar was often spotted sporting his signature bolo tie and cowboy hat while leading Interior.

The former Colorado attorney general, was thrust into the national spotlight in April 2010 when a blowout on the Deepwater Horizon rig caused an explosion that killed 11 workers in the Gulf of Mexico.

In the aftermath, BP's Macondo well spewed more than 4 million barrels of oil into the Gulf, as BP struggled to cap the well for nearly three months.

Facing an unprecedented environmental disaster, Salazar famously pledged to keep a "boot on the neck" of BP during the response efforts.

The catastrophe exposed shortcomings in the government's offshore drilling oversight, with officials conceding that regulations had not kept up with technological advances that allowed drillers to enter deeper and deeper waters.