Ride-hailing app Uber, under the microscope due to a handful of driver assaults on passengers in some cities, pledged in a blog post on Tuesday to sign up 1 million female drivers around the world by 2020.

The ride service did not provide comparable figures for how many women drivers are on the Uber service worldwide at present. In the United States, about 14 percent of its 160,000 drivers are female, the company said. Uber said it adds thousands more drivers each month.

"Uber does not require (minimum) hours, and it does not require a schedule," Salle Yoo, Uber's general counsel, said in an interview on Monday, referring to why women might find working for Uber attractive. "It offers the chance to be entrepreneurial, the chance to balance work and family."