Uber’s top executives, including its chief executive, Dara Khosrowshahi, have been on the road for the last week and a half, pitching institutional investors on the company’s stock. In recent days, that roadshow has coincided with turmoil in the stock markets. Over the last three days, the S&P 500 index fell partly over investor fears about the state of trade talks between the United States and China.

Choppiness in the stock market is among the biggest fears for bankers taking companies public, because that makes it harder to gauge where they should price a client’s shares. Even for a company as big as Uber, such volatility could affect its ability to command top dollar. Though Uber had initially planned to go public in the fall of 2019, it sped up its I.P.O. process to avoid the very situation it now finds itself in.

At the same time, Uber has had to answer investor questions about Lyft, its main North American rival. Lyft held its I.P.O. in late March, and its shares fell below its offering price on their second day of trading. As of Wednesday, Lyft’s stock was more than 26 percent below its $72 a share offering price.

Among the concerns that investors have expressed about Lyft — and which some share about Uber — are the steep losses that plague both companies, with limited visibility into when those losses will tail off, if ever. Ride-hailing is expensive, requiring plenty of spending to attract drivers and passengers. On Tuesday, Lyft reported a $1.14 billion loss for the first quarter.

Uber has said that it expects to lose money for years, as it tries to dominate in ride-hailing while also investing in new offerings like food delivery, electric bikes and scooters, freight and autonomous vehicles. The company recently said in a filing that it lost up to $1.1 billion in the first three months of this year alone.

Its public offering would nonetheless be a milestone for a generation of Silicon Valley start-ups that rooted their businesses in smartphones and pioneered a model known as the sharing economy, in which companies kept costs low by using freelancers to do the bulk of their work.

The companies have said that this model provides workers with flexibility. But the firms have since faced protests and lawsuits over wages and the lack of full-time benefits, including a global strike by ride-hailing drivers in cities from London to New York to San Francisco on Wednesday.