Uber investors value it at US$40b

New York

UBER Technologies Inc investors contend that the car-booking service is worth as much as US$40 billion - more than Twitter Inc and as much as Delta Airlines Inc.

While that is a big valuation, it may be justified by the size of the potential market and how richly other fast-growing technology companies are being valued.

The five-year-old start-up is close to raising a …