LOS ANGELES • Starbucks will close 8,000 company-owned US cafes for the afternoon on May 29 so that 175,000 employees can undergo racial tolerance training in response to protests and calls for boycotts after the arrest of two black men waiting in a Philadelphia store.

It said in an announcement on Tuesday that it will also provide training materials for non-company workers at the roughly 6,000 licensed Starbucks cafes that will remain open in locations such as grocery stores and airports.

The announcement from the world's biggest coffee company comes as it tries to cool tensions after the Philadelphia incident last week sparked accusations of racial profiling at the chain, which is the subject of a boycott campaign on social media.

The controversy is the biggest public relations test yet for new Starbucks chief executive officer Kevin Johnson, who already was fighting to boost traffic to the business amid competition from coffee sellers ranging from hipster cafes to fast-food chains and convenience stores.

"While this is not limited to Starbucks, we're committed to being a part of the solution," said Mr Johnson, a former technology executive who took the helm about a year ago.

Even if the threatened boycott does not materialise, the 8,000 temporary store closures will almost certainly have an impact on sales.

The coffee company did not say how many hours the stores would be shuttered on May 29, but the afternoon is the slowest time for its business.

Starbucks is one of the most high-profile and beloved brands in the world and its long-time CEO Howard Schultz was not one to shy away from difficult conversations over thorny issues such as gay marriage, gun control and congressional gridlock.

However, United States race relations have proven more challenging, even for a company that touts its diverse workforce - minorities account for 18 per cent of Starbucks executives with the title of senior vice-president or higher and 43 per cent of employees overall.

For example, the company's 2015 "Race Together" campaign to foster a conversation on the topic following the high-profile police shootings of several unarmed black men in the US stirred an intense social media backlash.

Mr Johnson apologised for the "reprehensible" arrests of the two men in Philadelphia last Thursday and took personal responsibility for the incident, which was captured in a customer video that was shared widely online.

Starbucks attorneys said Mr Johnson and the men, who were released without charges, have "engaged in constructive discussions about this issue as well as what is happening in communities across the country".

Philadelphia police late on Tuesday released the series of calls that led to the men's arrests.

It begins with a Starbucks employee reporting "two gentlemen in my cafe that are refusing to make a purchase or leave".

The manager who is believed to have made that call no longer works for Starbucks.

In a subsequent call, an unidentified man said a "group of males" was "causing a disturbance" that required backup and a supervisor.

Philadelphia's police commissioner over the weekend defended the arrests, saying that his officers had to act after Starbucks staff told them the pair were trespassing.

"It's good that Starbucks is giving all staff race training on May 29. But let's not lose sight of the real problem which is police accountability," said Ms Tiffany Dena Loftin, director of the youth and college division at the National Association for the Advancement of Coloured People.

REUTERS