US President Donald Trump has called for a boycott of Goodyear Tire & Rubber Co after claims the company has banned workers from wearing the “Make America Great Again” caps favoured by his supporters.

The Republican President, who is seeking a second term in office, said he would even change the Goodyear tyres on his presidential limousine if there was an alternative.

“Don’t buy GOODYEAR TIRES – They announced a BAN ON MAGA HATS,” he wrote on Twitter, referring to his slogan “Make America Great Again”, which is often emblazoned on baseball caps.

“I’m not happy with Goodyear because what they’re doing is playing politics,” Mr Trump said at a White House briefing on Wednesday.

Tweet from @realDonaldTrump

He said it was “disgraceful” the company would prevent employees wearing attire supporting the Blue Lives Matter movement that supports law enforcement, while allowing support for other causes which he described as “Marxist” in nature.

But Goodyear had not announced such a ban. All it had done was ask employees to refrain from workplace expressions involving political campaigns and “forms of advocacy that fall outside the scope of racial justice and equity issues”.

Despite that, Mr Trump’s tweet immediately sent the company’s stock downward.

His reaction followed a news report by TV station WIBW in Kansas about a training session at Goodyear’s headquarters that discussed political attire.

Goodyear said a widely circulated image that triggered the controversy was not created or distributed by the company’s corporate group.

The image spelled out appropriate and inappropriate displays, with Black Lives Matter and Lesbian, Gay, Bisexual, Transgender Pride deemed acceptable, while Blue Lives Matter and MAGA Attire were not.

“To be clear on our longstanding corporate policy, Goodyear has zero tolerance for any form of harassment or discrimination,” the company said.

Tweet from @goodyear

To enforce that policy, Goodyear said, it asked employees to avoid “workplace expressions in support of political campaigning for any candidate or political party as well as similar forms of advocacy that fall outside the scope of racial justice and equality issues”.

Shares in Ohia-based Goodyear, the largest tyre company in North America, fell after Mr Trump’s tweet and closed down 2.4 per cent.

Democratic challenger Joe Biden said Mr Trump’s comments showed he viewed thousands of jobs at Goodyear as “collateral damage” in another of his “petty political grievances”.

-with AAP