Former Homeland Security Secretary Kirstjen Nielsen said she resigned from the Trump administration because she refused to carry out certain directives she disagreed with.

Nielsen sat for an interview with PBS NewsHour substitute anchor Amna Nawaz at Fortune magazine's "Most Powerful Women" summit in Washington, D.C., on Tuesday.

"What led me to resign is there were a lot of things — that there were those in the administration who thought that we should do," Nielsen said, according to the Hill. "Just as I spoke truth to power in the very beginning, it became clear that saying no and refusing to do it myself was not going to be enough."

Nielsen still works in the Trump administration as an adviser.

President Trump announced Nielsen's resignation on April 7. At the same time, Nielsen posted her resignation letter on Twitter.

Nielsen had "determined that it is the right time for me to step aside," she said in her letter.

"I hope that the next Secretary will have the support of Congress and the courts in fixing the laws which have impeded our ability to fully secure America's borders and which have contributed to discord in our nation's discourse," she said.