US Vice President Mike Pence swore in former Texas Governor Rick Perry as US Energy Secretary during a ceremony at the White House on Thursday.
The US Senate on Thursday voted to confirm Perry, who has promised to renew America's nuclear weapons arsenal.
"President Trump called you to this role to serve as the 14th Secretary of Energy because of who you are because of what you've done. And because of what both of us and the people who know you well know you will do to lead the Department of Energy to even greater heights," Pence said before administering the oath of office.
Perry's rise to America's top energy official came against opposition from Democrats worried about his ties to oil companies, his doubts about the science of climate change, and the fact that he once called for the department's total elimination - a comment he has since said he regrets.
Perry, 66, was governor of Texas from 2000 to 2015, making him the longest-serving governor of the oil-producing state in its history.