Former Defense Secretary Donald Rumsfeld publicly announced his support for Donald Trump for president during an interview with Fox News host Greta Van Susteren late Wednesday.

"I could not vote for Mrs. Clinton," Rumsfeld said.

"All right. Are you endorsing Trump or supporting him? Voting for him?" Van Susteren followed up.

"I don't know that there's any difference," Rumsfeld responded.

"So this is an endorsement?" the host asked.

"No, I don't — one asked me for my endorsement, but I'm clearly going to vote for him. I mean, there's — I just can't imagine not," Rumsfeld said.

Rumsfeld said he agrees with the presumptive Republican nominee on reforming the NATO alliance, temporarily banning Syrian refugees and other policy views.

Rumsfeld is the highest-ranking member of the George W. Bush administration to endorse Trump.