Donald Trump

Republican presidential candidate Donald Trump gestures during a campaign event in Hartford, Conn., Friday, April 15, 2016. (AP Photo/Charles Krupa)

(Charles Krupa)

United Auto Workers President Dennis Williams speaks in July as General Motors CEO Mary Barra, background left, listens during a ceremony to mark the opening of contract negotiations in Detroit. UAW members at General Motors appear poised to approve a new four-year contract with the company. Workers at two union locals at a huge factory in Lordstown, Ohio, east of Cleveland, and at an SUV assembly plant near Lansing, Michigan, voted overwhelmingly for the deal on Friday, Nov 6, 2015.

DETROIT - The UAW has not formally endorsed a candidate for president of the United States, but one thing is certain: It will not back Donald Trump.

UAW President Dennis Williams told reporters at a media roundtable Thursday morning that the union took issue with some of Trump's comments on moving automotive jobs from Michigan to non-union states, in order to compete with low-wage labor in Mexico.

He was referring to Trump's interview with the Detroit News last August, in which the Republican candidate said this:

"You can go to different parts of the United States and then ultimately you'd do full-circle -- you'll come back to Michigan because those guys are going to want their jobs back even if it is less," Trump said. "We can do the rotation in the United States -- it doesn't have to be in Mexico." He said that after Michigan "loses a couple of plants -- all of sudden you'll make good deals in your own area."

Williams said this would further exasperate an income inequality problem in the U.S.

"I don't know how that's helping the middle class or how that's helping American workers, and it's certainly not helping UAW members," Williams said. "That's the wrong kind of leadership. So we ruled him out real quick."

A message seeking comment from the Trump campaign was left Thursday morning.

Williams said the executive board for the UAW sent surveys to all presidential candidates, and only Democrats responded.

While the UAW has not thrown its weight behind a single candidate, Williams said Democratic candidates Bernie Sanders and Hillary Clinton "both bring a lot to the table."

He said Clinton is "certainly the front-runner at this point" in the race for the Democratic nomination, and he noted that in 2008, when Barack Obama was leading in pledged delegates heading toward the summer convention, the two candidates sat down and agreed to do what was best for the party.

"I expect no less of Bernie Sanders and Hillary Clinton," Williams said.