WASHINGTON — A top military adviser to Donald Trump is being vetted to be his running mate, The Post has learned.

The outspoken and brash Lt. Gen. Michael Flynn — who was forced out of his post by the Obama administration in 2014 after pointing out the rising global jihadist threat — has already briefed the Republican presidential candidate on several occasions and is in close touch with high levels of Trump’s staff.

Flynn joins the ranks of GOP politicians being looked at for the high-profile pick, including former House Speaker Newt Gingrich, Sen. Jeff Sessions of Alabama, New Jersey Gov. Chris Christie, Indiana Gov. Mike Pence and Sen. Joni Ernst of Iowa.

Trump spent the holiday weekend with two of the contenders.

“Spent time with Indiana Governor Mike Pence and family yesterday,” Trump tweeted Monday morning. “Very impressed, great people!”

Later, Trump revealed he would be visiting Monday with Ernst, a rising Republican star.

Although Flynn, the former head of the Defense Intelligence Agency, made a name for himself speaking out against his former boss, he is not treating his potential future boss the same way.

“One of the things I expect Mr. Trump would look for in a vice president is discretion,” Flynn told The Post, coyly declining to comment on being vetted by Trump.

“All I would say is that I have been honored to serve my country for the past three decades and look forward to serving in other ways now that I am retired from the US Army,” he said. “I’ve been a soldier too long to refuse to entertain any request from a potential commander in chief.”

Trump praised Flynn in a statement to The Post.

“I have a lot of respect for Gen. Flynn, and his advice is important,” he said.

The general’s debut book, “The Field of Fight: How We Can Win the Global War Against Radical Islam and Its Allies,” which hits shelves July 12, offers a grim but realistic view of the global jihadist threat.

“We’re in a world war,” Flynn wrote in the introduction of his book, according to early excerpts.

“We could lose. In fact, right now we’re losing,” he wrote. “To make matters worse, our political leaders insist that the war is going very well, and the scores of professional analysts who know better are being censored when they report the truth to their superiors.”