SAO PAULO (AP) — Thousands of drivers from Uber and cabbies faced off in Brazil's capital Tuesday as the Senate voted to soften proposed new regulations that the ride-sharing app said would sink its business in its second-largest market worldwide.

In the latest threat to Uber's global business, senators debated a bill passed in April by Congress' lower house that called for municipal governments to regulate ride-sharing apps, including requiring insurance for carrying passengers and pension benefits for drivers. It also had requirements for increased oversight of drivers and their cars.

Hundreds of cabbies as well as drivers for Uber and other ride-sharing apps followed the session from the hallway, cheering those who spoke in favor of their positions. Some drivers called out the names of senators who disagreed with them and booed. Outside, police used pepper spray and formed a human cordon to separate thousands more drivers from both sides who had been shouting at one another.

Senate President Eunicio Oliveira said senators could not accept the legislation as written and wanted to find a compromise balancing the interests of the two types of drivers, one that "doesn't crush one and doesn't crush the other."

Late Tuesday night, the Senate made amendments to the bill, meaning it will go back to the lower Chamber of Deputies for further consideration.

The Senate threw out a requirement that Uber cars have red license plates like taxis and that Uber drivers be owners of the vehicle they drive. It wasn't immediately clear how those changes would be received by the lower house.

Congressman Carlos Zarattini, who wrote the original bill, had acknowledged that the measure as passed by his house would likely end ride-sharing as it currently existed, but he and other lawmakers said the apps offer too little protection for their drivers.

Among the other contentious points was a requirement that drivers get an authorization from the city in which they operate. That could mean drivers couldn't take passengers from Sao Paulo, for instance, to the city's international airport, which is in another municipality.

Uber had called the changes a "covert ban" and said they would make business in Latin America's largest nation unviable. It launched a lobbying campaign against the bill, collecting the signatures of more than 800,000 Brazilians who say they oppose it.

Uber has faced similar challenges in other countries. Last month, London's transport regulator stripped Uber of its license, though the company continues to operate while it appeals. It has been the subject of litigation in France, where it has been banned from offering rides with non-professional drivers. It is fighting new regulation in Quebec and threatened to pull out of that market.