President Trump said in an interview broadcast Thursday that NFL owners are “afraid of their players,” his latest provocative comments in a crusade against those who take a knee during the national anthem.

Trump urged the football league to adopt and enforce a rule that requires players to stand during the anthem. He said he has talked in recent days to several team owners, who he said are “in a box” on the issue.

“I think they’re afraid of their players, if you want to know the truth, and I think it’s disgraceful,” Trump said in an interview broadcast on “Fox & Friends” on Fox News. “They’ve got to be tough, and they’ve got to be smart.”

The interview was recorded Wednesday in Indianapolis before Trump’s speech on a Republican-crafted tax plan.

Trump stoked a national controversy Friday when he criticized NFL players who kneel during the national anthem, using a profane term to describe them. He has continued to highlight the issue in tweets and public comments every day since.

Colin Kaepernick, a former San Francisco 49ers quarterback, started the form of protest last year as a means to draw attention to police killings of unarmed black people and oppression of minorities.

Most of the players who have knelt are African American. Trump has said his comments have nothing to do with race but are about respecting the country and the flag.

On Sunday, teams across the NFL locked arms, with some kneeling and some staying in their locker rooms, in displays of unity aimed at Trump’s comments. Several team owners participated in the gestures, which continued Monday at a game in Phoenix.

Trump’s latest comments prompted a rebuke Thursday from Rashad Robinson, executive director of Color of Change, a political advocacy group for African Americans.

“Trump's comments that NFL owners are 'afraid of their players' is a blatant dog whistle,” Robinson said in a statement. “This language is dangerous and shameful, and must be roundly condemned by NFL owners.”

At a news briefing Thursday, White House press secretary Sarah Huckabee Sanders was asked to explain what Trump meant by “afraid of their players.”

“Probably the backlash of the players and the stance that they're making, and, you know, not wanting to create that conflict within their team,” she said.

“The president is here to lead the country,” she added. “ He feels very strongly about this, as do most Americans because they certainly agree with him, as we've seen not just in the public support, but also in public polling on that very specific issue.”