The war of words between Uber and City Hall on a proposed black and livery car cap escalated over the weekend, while labor unions and civic groups prepared to push back against the app company Monday.

The City Council proposed two bills last month to strongly limit the number of new for-hire vehicles, as well as to study the rapidly rising industry's impact on traffic. A vote in the City Council could happen as early as Thursday.

Uber, which strongly opposes the bills, has been using its app to urge users to send messages to City Hall that say the legislation would worsen waits for passengers and take away job opportunities.

Deputy Mayor Anthony Shorris fired back with a message on Friday that said Uber is spending millions on a misleading political campaign.

"There are serious questions about how Uber treats its customers, its workers, and whether it is flooding New York City's already heavily-crowded streets with thousands of more vehicles," he wrote in a reply email to Uber users.

An Uber executive wrote back to Shorris on Sunday in an open letter arguing that its 6,000 Uber cars out during an average hour are a small part of the city's overall traffic.

"With 25,000 New York City residents taking their first ride each week, the number of driver-partners needs to increase rapidly or Uber will no longer be the service people know and love," wrote Josh Mohrer, the app's general manager in New York City.

He added that all drivers are licensed by the Taxi and Limousine Commission and features of the app like GPS make Uber safer than other services.

The heated words follow Uber taking out television ads last week that said the cap would cost 10,000 jobs -- and adding a 'de Blasio' tab to their app that shows no cars on its virtual map.

Councilman Ydanis Rodriguez, who chairs the transportation committee, will push back at Uber at City Hall Monday with groups that include labor unions like the New York Taxiworkers Alliance and the Transport Workers Union Local 100.

The TWU Local 100, which reps transit and Citi Bike workers, will call for black and livery car trips to include an MTA tax like yellow cabs.

"The growth of Uber and other app-based for-hire vehicle services has worsened pollution, made streets less safe, diverted revenue from public transit services and created part-time poverty wage jobs," the union said in a memo of support for the two bills.

The New York Taxi Workers Alliance, which includes several thousand Uber drivers, backs the cap and says increased competition for fares is hurting all drivers.

"It is a desperate, fast track to poverty for thousands of working men and women who can least afford it," said its executive director Bhairavi Desai at a recent City Council hearing.