Republican presidential hopeful Donald Trump said Sunday he doesn't watch professional football much anymore because the NFL has gone "soft" like the United States.

The billionaire also told about 3,000 people during a Reno rally he believes he's leading in Iowa, New Hampshire and Nevada, and if he wins Iowa's first-in-the nation caucuses next month "we're going to run the table."

Trump drew the football analogy during a campaign speech in a downtown ballroom while casino sportsbooks were jammed with fans across the street watching the NFL playoffs.

"Football has become soft like how the country has become soft," he said.

In recent years, the NFL has implemented various rules aimed at curtailing concussions among players amid rising concern over football safety, such as 15-yard penalties in many cases for helmet-to-helmet collisions and head-to-head blows.

"What used to be a violent hit, a great tackle," he said, now results in penalties never called in the past against such Hall of Famer defenders as Dick Butkus and Lawrence Taylor. "You used to see these tackles and it was incredible to watch. Now the whole game is so screwed up."

Trump said he's seen the same thing happen to superpowers around the world throughout history.

"They become soft, they became weak and they disappeared," he said. "If I become president of the United States, we are going to be so strong."