Howard Schultz, who built a small Seattle coffee chain into the global powerhouse Starbucks, announced on Monday he was retiring from the company, fueling speculation he may seek the Democratic presidential nomination in 2020.

Schultz, 64, has been serving as executive chairman of Starbucks since stepping down as chief executive in April of last year and handing over to Kevin Johnson.

Schultz will leave the company at the end of the month and take on the honorary title of chairman emeritus, Starbucks said in a statement.

Schultz's announcement triggered immediate speculation that he may consider entering politics as a Democrat and run for the White House two years from now.

Schultz told The New York Times he hadn't decided on his next move yet, but “for some time now, I have been deeply concerned about our country - the growing division at home and our standing in the world".

Schultz, who has been openly critical of President Donald Trump, said: “One of the things I want to do in my next chapter is to figure out if there is a role I can play in giving back.

“I intend to think about a range of options, and that could include public service,” he said, when asked if he was weighing a presidential run.

“But I'm a long way from making any decisions about the future.

“I want to be of service to our country, but that doesn't mean I need to run for public office to accomplish that,” Schultz told the The New York Times.

Schultz joined Starbucks in 1982 as director of operations and marketing and helped transform the Seattle-based company into a global behemoth with more than 28,000 outlets in 77 countries.

“I set out to build a company that my father, a blue-collar worker and World War II veteran, never had a chance to work for,” Schultz said in an open letter to past and present Starbucks employees.

“Together we've done that, and so much more, by balancing profitability and social conscience, compassion and rigor, and love and responsibility.”

Racial bias awareness training

In its statement, Starbucks did not mention any political ambitions for the departing executive but said Schultz was “looking forward to spending more time with his family this summer".

“He is also writing a book about Starbucks social impact work and the efforts to redefine the role and responsibility of a public company in an ever-changing society,” it said.

Schultz's departure comes a week after the company closed more than 8,000 US stores to provide racial bias awareness training to around 175,000 employees.

The move followed the April 12 arrest of two black men in a Philadelphia Starbucks, which sparked outrage, protests and soul-searching about racial tensions that have been exacerbated under President Trump.

Speaking to CNN about the closure, Schultz said “we realise that four hours of training is not going to solve racial inequity in America or anyone coming into our stores who may have a problem.

“But we have to start the conversation.” Starbucks shares were down 1.31 per cent to $56.32 in after-hours trading on Wall Street.