Rick Perry has been sworn in as President Donald Trump's energy secretary.
The former Texas governor was approved by the Senate earlier by a 62-37 vote, and was sworn in at the White House by vice president Mike Pence.
Mr Perry, who once pledged to eliminate the Energy Department, has repeatedly promised to be an advocate for the agency and to protect the nation's nuclear stockpile.
He has also said he will rely on federal scientists including those who work on climate change.
He has pledged to work to develop US energy in all forms, from oil, gas and nuclear power to renewable sources such as wind and solar.
Democrats said they have accepted Mr Perry's disavowal of his 2011 pledge to abolish the department, but they claim they are worried he may not stand up to Republican proposals to slash the budget.