A US sporting goods business has been forced to close its doors after the owner decided to stop selling Nike products to protest against the company's decision to use former NFL star Colin Kaepernick in an advertising campaign.

Key points: Sporting apparel giant Nike's 2018 ad campaign featuring ex-NFL star Colin Kaepernick was highly controversial

Sporting apparel giant Nike's 2018 ad campaign featuring ex-NFL star Colin Kaepernick was highly controversial Kaepernick has not played in two years for kneeling for the national anthem at NFL games

Kaepernick has not played in two years for kneeling for the national anthem at NFL games A sporting goods business in Colorado has closed five months after banning Nike goods in protest at the ads

Owner Stephen Kurtis Martin wrote on Facebook, "Prime Time Sports is closing".

"Thank you for 21 mostly good years," he added, admitting the Colorado business could not afford to stay open without stocking Nike apparel.

Nike stoked controversy in September last year when it used the former San Francisco 49ers quarterback in its latest Just Do It campaign.

Kaepernick has not played in the NFL since 2016 when he knelt during the national anthem of a pre-season game to protest against the treatment of black people in the United States, earning the ire of supporters and politicians.

Colin Kaepernick (right) has not played in the NFL since kneeling during the national anthem. ( AP: Jose Sanchez )

The Nike advertisement showed Kaepernick staring at the camera with the slogan, "Believe in something. Even if it means sacrificing everything," leading to a fierce backlash on social media, with some people going so far as to burn their Nike products.

Nike's advertising campaign featuring Colin Kaepernick proved divisive. ( Supplied: Nike )

Mr Martin followed suit, slapping "half price" tags on all his remaining Nike products and refusing to stock Nike products in the future.

"Being a sports store without Nike is kind of like being a milk store without milk or a gas station without gas," Mr Martin told a local television station.

"How do you do it? They have a monopoly on jerseys."

When announcing the store's boycott in September Mr Martin wrote that he believed Kaepernick sacrificed "a salary" as opposed to "everything".

The owner boycotted Nike for highlighting Colin Kaepernick's decision to kneel for the national anthem at NFL games. ( Facebook: Stephen Kurtis Martin )

"I am still choosing to stand. Still choosing to honor (sic) our flag and anthem for what they represent, no matter what the cost is to me because I too 'believe in something, even if it means sacrificing everything'," Mr Martin wrote.

"To me, it is nothing compared to each story behind every photo that I personally read that built our precious 'Honor The Flag Memorial Wall'.

"We have a choice. We have a voice. And I am choosing not to be a Nike dealer anymore."

However, that decision backfired, prompting the store to close its doors just five months later.