Newt Gingrich says that he thinks Donald Trump is a "necessary candidate" amid global anti-establishment sentiment, but that he wouldn't automatically say yes to an eventual proposal to become Trump's running mate.

The former House Speaker said in an interview Saturday with The Associated Press that he thinks Trump will make his choice Thursday or Friday ahead of the Republican convention.

Gingrich said he has been vetted but accepting to partner with Trump, "It's not an automatic Yes."

Gingrich said the British vote to leave the EU is part of "a worldwide movement toward really being angry at the establishment ... really feeling that government has failed and I think Trump is part of that worldwide movement."

Gingrich was at a giant annual gathering of the People's Mujahedeen of Iran opposition group outside Paris.