The London Underground and Rail, Maritime and Transport are holding last-ditch talks just hours before a three day strike, that could affect millions of people across London and surrounding areas.
Conciliation service Acas said the talks between the RMT and London Underground started at 10am.
RMT union members are set to walk out of their jobs for three days at 9pm this evening, in a long-running dispute with the London Underground over ticket office closures.
A two-day strike last week caused huge disruption, with roads clogged as people switched to other forms of transport.
More top news
The World Health Organization said postponing the 2016 Games would not 'significantly alter' the spread of the Zika outbreak.
Employment Minister Priti Patel has launched a scathing attack on the government's 'chaotic' immigration controls.
Hanako died peacefully in a Tokyo zoo after living alone for 67 years.