Ride-hailing firm Uber Technologies Inc. has agreed to sell its Southeast Asian business to bigger regional rival Grab, a source with direct knowledge of the matter said on Sunday, in what would be the U.S. company's second retreat from Asia.

The deal, which could be announced as early as Monday, marks the first big consolidation in the industry in Southeast Asia, home to about 640 million people, and will put pressure on rivals such as Indonesia's Go-Jek, backed by Alphabet Inc.'s Google and China's Tencent Holdings Ltd.

As part of the transaction, Uber would get a stake of as much as 30 percent in the combined business, the source said. He did not want to be identified as the deal is not public yet.