Talks aimed at reaching a pay deal for London Underground (LU) workers have "collapsed", raising the threat of industrial action.
Leaders of the Rail, Maritime and Transport (RMT) union met with the company, which has offered a two-year pay deal worth RPI inflation plus 0.1% followed by RPI plus 0.2%.
The union said it was moving to a strike ballot after complaining that LU had not improved its offer.
General secretary Mick Cash said: "The failure of Tube bosses to come up with proposals that meet our call for serious improvements in both pay and working conditions has been the catalyst for the collapse of the talks today.
"That failure by the management side means we have no option but to accelerate the balloting process and escalate the dispute.
"RMT is angry and frustrated that the company have opted to ignore the massive contribution tube staff make to this city, delivering services, including the night tube, often in difficult operational conditions.
"RMT remains available for further talks but no-one should underestimate our determination to secure a pay and conditions deal that reflects the huge contribution of all London Underground staff."
The union announced earlier it was preparing to ballot its members on the Tube to combat plans to privatise parts of the waste collection service.
It warned that jobs are under threat from "creeping cuts" under Transport for London's (TfL) so-called transformation programme.
The RMT said it has been told that the programme will lead to job cuts, as well as privatising bin collection and transportation on parts of the Tube network.
A TfL spokesman said: "Although no final decision has been made, we have been reviewing our waste collection services and have identified the potential to make them more efficient and cost-effective in the places where collection rates are low.
"The higher intensity collections within zones 1 and 2 will remain with our in-house team. These proposals will result in no compulsory job losses for any of our existing staff and we will continue to discuss the plans with our unions."
A Transport for London spokesman said:
"We have made an offer to our unions that we believe is fair and affordable. We remain available for further discussions and have asked that Acas help to facilitate these talks."We look forward to finding a resolution in order to provide certainty for our hardworking staff."