Lonnie Bunch III said he will retire as the head of the Smithsonian Institution, a role that placed him at the center of President Donald Trump’s efforts to reshape the world’s largest museum organization.

“It is with very mixed emotions and heartfelt gratitude that I announce my retirement from the Smithsonian,” Bunch said in a statement on Tuesday, adding, “I leave with pride and sadness, gratitude and joy, and with enormous confidence in the people who will carry this remarkable institution forward.”

Bunch, 73, said in multiple interviews that his retirement was not related to pressure from the Trump administration to make changes to the institution.

It still comes as the Trump administration has increased pressure on the institution, including saying in an August 28 letter that federal agencies may stop working with the Smithsonian if its leadership does not change. The letter cited an earlier report that accused the Smithsonian of moving “toward an extreme political activism that seeks to transform our country.”

CNN has reached out to the White House for comment.