Sen. Ron Johnson, R-Wis., said he disagrees with Donald Trump’s proposal to ban Muslims from entering the United States, and said the best way to curb terrorist events in the U.S. is to work more closely with Muslim groups.

Trump, the presumed GOP nominee, renewed call his call a ban on Muslim immigration following Sunday’s terror attack at a gay nightclub in Florida. But Johnson argued that the root cause of terrorism is “Islamic terror groups,” he said in a Monday interview with Green Bay talk radio host Jerry Bader.