SoftBank Group Corp. and a group of investors are said to be trying to buy a big stake in Uber Technologies Inc. at a sizable discount to the ride-hailing company's $69 billion valuation, seeking to clinch what would be one of the largest ever purchases of stock in a private company.

SoftBank and partners including investment firms Dragoneer Investment Group and General Atlantic are offering to spend more than $6 billion for a stake that would value the ride-hailing company at $48 billion, or about 30 percent lower than the valuation it fetched in its most recent round of fundraising.

If it is successful, the SoftBank-led coalition would buy at least 14 percent of the shares from existing Uber investors. The share purchase, along with an additional $1 billion direct investment in the company, would make the group one of Uber's biggest shareholders, according to sources who asked not to be identified discussing the private terms.