Forget Kim Jong-Un - the president of the USA has a new high-profile opponent: NFL players' moms.

On Thursday the Professional Football Players' Mothers Association (PFPMA) blasted Donald Trump for referring to players engaging in protests over racial violence as 'sons of b*****s'.

They accused him of promoting 'anger and hatred' and demanded 'a stop to the divisive language' In an open letter obtained by BuzzFeed News.

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The Indianapolis Colts were among several teams whose players kneeled during the national anthem on Sunday as part of ongoing protests against police brutality against black people

On September 22, Trump called the protesters 'sons of b*****s' while promoting Luther Strange's failed Senate run (Trump pictured at event) - so the NFL moms' association took him to task on Thursday in an open letter about his 'inflammatory language'

Trump made the remarks on September 22 at a rally supporting Luther Strange's failed bid for the Senate.

He was commenting on NFL players who are kneeling through the national anthem in a peaceful protest against police brutality.

'Wouldn't you love to see one of these NFL owners, when somebody disrespects our flag, to say, "Get that son of a bitch off the field right now"?' Trump said to the cheering crowd. 'Out. He's fired. He's fired.'

He's continued making similar remarks in the week since.

In response, the PFPMA said: '[We] believe in promoting a positive image of professional football players as athletes and young men of character.

'It saddens the organization to know that President Donald Trump would make our sons - as well as their mothers - the target of inflammatory, offensive comments that are intended to promote anger and hatred, depleting them of their heritage and self-identity.'

Michele Green, president of the association (pictured with son and ex-NFL player Bryant McKinnie), was among those who said Trump's remarks were 'intended to promote anger and hatred'

They said that 'won't work' and that their sons would 'continue to present themselves in a positive image,' while commending the fans and NFL staff that have promoted the players' protests.

'Whether it be by kneeling or standing with their arms locked, our sons have chosen this platform to get the message out about social justice and unity, and they will always have our support,' it continues.

'Now that we obviously have your attention, let’s put a stop to the divisive language and start a productive dialogue for positive change.'

The letter ends with a pointed passage from Proverbs: 'Whoever keeps his mouth and his tongue keeps himself out of trouble.'

Michele Green, PFPMA's president and mom of former Minnesota Vikings offensive tackle Bryant McKinnie, said that she had been personally offended by Trump's comment, which she saw as bullying.

'We know our self-worth as mothers,' she told BuzzFeed News. 'We're not what he said we were.'

Thursday night's game between the Green Bay Packers and Chicago Bears began with both teams linking arms in what they described as a 'show of unity and love'.

They invited the crowds to join in - shying away from calling it a protest - but the fans were divided in their response.

Some in the stands mimicked them, joining arms in the stands as they sung along.

But many remained unaffected and held American flags and signs complaining about the ongoing protest of NFL players during prime-time games.