Uber and Transport for London are to hold further peace talks after failing to reach an agreement at a summit where the ride-hailing app’s chief executive launched an attempt to win back its licence.

Dara Khosrowshahi, who took over as Uber CEO in August, flew to London for the emergency meeting with the TfL commissioner, Mike Brown, on Tuesday. The pair are understood to have discussed measures Uber could take to resolve the dispute, during head-to-head talks that ended without the US company making any commitments.

A TfL spokesperson said: “Today’s constructive meeting centred on what needs to happen to ensure a thriving taxi and private hire market in London where everyone operates to the same high standards. Further steps in this process will take place over the coming weeks.”

Uber also hailed the meeting as constructive, saying: “We hope to have further discussions over the coming weeks as we are determined to make things right in London.”

After the meeting Khosrowshahi tweeted a picture of himself with some Uber drivers, saying he was “determined to make things right in this great city”.

Khosrowshahi’s personal intervention came after TfL refused to renew Uber’s licence to operate in London, saying it was not “fit and proper” due to concerns including safety checks on drivers and its attitude to reporting crimes.

While talks with TfL about a potential rapprochement are to continue, Uber has until 13 October to lodge a legal appeal against the transport authority’s decision. Its drivers can keep operating until then and potentially after that date if the appeal process is extended.

TfL’s decision proved divisive, with Theresa May calling the move “disproportionate” and saying the London mayor, Sadiq Khan, who chairs TfL, had “damaged the lives” of the 40,000 Uber drivers operating in the capital.

Within days of the decision, more than half a million people had signed a petition calling for the reinstatement of Uber’s licence to operate in London, where it has 3.5 million registered users.

Unions such as the IWGB have called on TfL to insist that Uber guarantee basic employment rights under the terms of a new five-year licence, although the IWGB said revoking the licence was a step too far due to its impact on drivers.

James Farrar, who chairs the IWGB’s minicab drivers’ branch and is a co-claimant in an employment tribunal case against Uber, criticised the secretive talks.

“It’s clear that Uber chief executive Dara Khosrowshahi and TfL are just going through the motions to give people the impression that they are both doing something to clean up Uber’s act,” he said.

“The reality is that neither seems to want to talk to the main stakeholders in the business – the drivers – or deal with their concerns.

“Until they do that, we can expect the company will continue to flout UK employment law and deny their drivers basic worker rights.”

Khosrowshahi’s arrival was partly overshadowed by the resignation of Jo Bertram, the head of Uber in northern Europe, who had ultimate responsibility for the San Francisco-based company’s London outpost. Uber said her decision had nothing to do with the revocation of its licence.

• This article was amended on 6 October 2017. An earlier version said that the IWGB had praised TfL’s decision, when that union criticised it.