Uber passengers in Canada may soon find themselves facing a classic service industry conundrum: "How much should I tip?"

In an announcement to U.S. Uber drivers on Tuesday, the ride-hailing service said it will roll out a tipping function for its app in all U.S. cities by the end of July. The tipping option is already online in Seattle, Minneapolis and Houston, Uber said.

The ability to tip Uber drivers through the Uber app is likely coming to Canada by the end of the year, suggested Uber Canada spokesperson Susie Heath.

"Nearly every feature we are building and shipping over the next 180 days is being built for a global audience, and many — if not most — will be available internationally by the end of the year," wrote Heath in an email.

In addition to tipping, Uber announced a number of other changes for U.S. drivers, including shortening the period of time during which passengers can cancel rides without paying a cancellation fee, and paying per-minute wait fees to drivers who wait for a passenger for more than two minutes.

Uber operates a cash-free business model, charging fares directly to users' credit cards through the Uber app. Lyft, Uber's main rival in the North American ride-hailing space, has long offered the option to tip its drivers through the Lyft app.

In April, New York's Taxi and Limousine Commission took steps toward requiring Uber to offer an easy tipping option, after a petition from a group of New York City drivers.

Public relations challenges

Uber is working to improve its relationships with drivers amid a series of challenges to the company's reputation.

CEO Travis Kalanick recently stepped away from the company following an internal investigation into allegations of sexism and sexual harassment at Uber. The probe, which resulted in the termination of 20 Uber employees, followed an explosive blog post by Susan J. Fowler, a former Uber employee who described a culture of sexual harassment at the company.

Uber also recently fired a high-profile autonomous-driving researcher who was alleged to have stolen trade secrets from the self-driving car company Waymo, which is suing Uber.

The company is also facing a criminal probe from U.S. authorities over the use of "Greyball," a software tool that was used to stymie regulatory efforts against Uber by local authorities.

Some of Uber's recent negative press has focused on its relationships with drivers.

In February, CEO Kalanick was caught on camera arguing with an Uber driver who was complaining about Uber's business practices. In late May, Uber admitted that it owed its drivers in New York City tens of millions of dollars.