Kalanick said in a statement first reported by the New York Times and verified by an Uber spokesman that he loved Uber more than anything, but he accepted the investors' request to step aside so that Uber can go back to building rather than be distracted with another fight.

Kalanick, 40, has faced increased scrutiny in recent weeks following an investigation into the culture and workplace practices at a company he helped start in 2009 and is now the world's most highly valued startup.

But it was a chorus of demands for changes at the top from some of Uber's biggest investors that ultimately forced Kalanick out,.

Venture capital firm Benchmark, whose partner Bill Gurley is one of Uber's largest shareholders and sits on its board, as well as investors First Round Capital, Lowercase Capital, Menlo Ventures and Fidelity Investments, all pressed Kalanick to quit.

They delivered a letter to Kalanick while he was in Chicago, the New York Times reported, citing people with knowledge of the situation. The newspaper, which was first to report Kalanick's resignation, said he would remain on Uber's board.

Kalanick's departure comes after a lengthy investigation led by former US Attorney General Eric Holder. Uber hired Holder to look into its culture and workplace practices after a female former employee publicly accused the company of what she described as brazen sexual harassment.

Kalanick said last week he would take a leave of absence for an undetermined period. He said he needed space to grieve the death of his mother, who died recently in a boating accident in which his father was also seriously injured, and to work on his leadership skills.