SAN FRANCISCO — A group of Uber’s largest shareholders have agreed to sell a significant stake in the ride-hailing giant at a steep discount, according to two people familiar with the process who were not allowed to comment on it publicly.

The sale is a big step for the company as it looks to calm investors and pave the way for an initial public offering in 2019.

SoftBank Group and a consortium of investors plan to purchase 17.5 percent of Uber at a price of about $33 a share. That puts the value of the company at about $48 billion — a notable drop from the near $70 billion valuation Uber had commanded about a year and a half ago.

“We look forward to working with the purchasers to close the overall transaction, which we expect to support our technology investments, fuel our growth, and strengthen our corporate governance,” Matt Kallman, an Uber spokesman, said in a statement.