Uber has been asking to meet Sadiq Khan, the mayor of London, since his election in May 2016 but those requests have been rejected, according to sources close to the US company.
It has 21 days to appeal TfL's decision and can continue to provide its services in the capital "until the appeals process has been exhausted" - a point Mr Khan reiterated in a response to the change.org petition (more than 680,000 people have signed an online petition in a bid to keep Uber operating in London after its licence expires on 30 September).
TfL cited failures to report serious criminal offences, conduct sufficient background checks on drivers and other safety issues as grounds for not renewing Uber's licence.
Uber said in a series of tweets on Sunday that it would challenge the TfL decision "in the courts to defend the livelihoods of drivers & the consumer choice of millions of Londoners who use Uber".
"Drivers who use Uber in London are licensed by TfL and have been through the same enhanced DBS [Disclosure and Barring Service] background checks as black cab drivers.
"We have always followed TfL rules on reporting serious incidents, with a dedicated team that works closely with the Metropolitan Police."