Talks aimed at averting strikes by London Underground workers over Tube ticket office closures are to be held.
Members of the Rail, Maritime and Transport (RMT) union are due to stage two 48-hour walkouts next month in protest at the closures and the loss of hundreds of jobs.
The Transport Salaried Staffs Association is balloting its members, with the likelihood of co-ordinating industrial action, which would cause travel chaos in the capital.
RMT general secretary Bob Crow said the conciliation service Acas had convened a meeting tomorrow.
He said: "RMT will enter the talks in good faith and we hope that the company are serious about conciliation and not just going through the motions and playing games when so much is at stake for Tube users and staff."
Phil Hufton, LU's chief operating officer, said: "We've been clear that our customers and staff are at the heart of our vision for the future of the Tube. All Tube stations will remain staffed at all times when services are operating, and we'll be introducing a 24-hour service at weekends during 2015.
"In future, there will be more staff in ticket halls and on platforms to help customers buy the right ticket and keep them safe and secure.
"We're committed to implement changes to station staffing without compulsory redundancies and we've been clear that there'll be a job for everyone at LU who wants to work for us and be flexible.
"We will be seeking to re-affirm these commitments to the unions later this week and are urging them to proceed with the consultation that is under way without threatening to disrupt Londoners."
LU managing director Mike Brown urged TSSA union leader Manuel Cortes to call off the ballot for industrial action, saying that the union openly supported the main elements of LU's plans to improve customer service. "I fully endorse TSSA's priorities to improve customer service," he said.
"Given this, it seems very strange and completely unnecessary for the TSSA leadership to be balloting its members for strike action and all the disruption to Londoners that would entail.
"I have already committed to delivering improvements to customer service with no compulsory redundancies. There will continue to be a job for anyone who wants to remain and is willing to be flexible and work with us to build a Tube service fit for London in the 21st century.
"I am therefore urging the TSSA leadership to abandon the proposed strike ballot without delay and work with us to help shape the future of the Tube."
Mr Cortes said: "Coming four days into our ballot, this is a cynical attempt to persuade our members to vote no by the time voting finishes next Monday.
"The statement makes no mention of the 953 jobs being axed and the removal of permanent station supervisors."