Uber posted a loss of $1.07bn (£821m) in the three months to September, as the ride-sharing firm prepares for a public stock offering next year.
The US company's net losses widened sharply on a quarterly basis as revenues rose only slightly.
Uber was recently valued at $72bn, making it one of the most valuable privately held firms in the world.
But it is under pressure to become more profitable for a planned offering of its shares to the public next year.
Net losses widened sharply to $1.07bn from $891m, figures from Uber showed, as revenues and bookings rose only slightly.
But losses were down 27% compared to the same period last year, according to Reuters.
"We had another strong quarter for a business of our size and global scope," Uber chief financial officer Nelson Chai said in a statement.
"As we look ahead to an IPO and beyond, we are investing in future growth across our platform, including in food, freight, electric bikes and scooters, and high-potential markets in India and the Middle East where we continue to solidify our leadership position."
Revenues rose by 5% on the previous quarter to $2.95bn, while gross bookings were up 6% at $12.7bn.
Bookings growth slid into the single digits on a quarterly basis at the start of this year, Reuters said.
Japan's Softbank has taken a 15% stake in Uber in a deal which foresees an initial public offering by Uber next year.