Talks aimed at resolving the year-long dispute over staffing and driver-only trains on Southern Railway are to resume.
Leaders of the Rail, Maritime and Transport union will meet with company bosses today in a bid to break the deadlocked row.
RMT members have taken 31 days of strike action over the past year, with further stoppages not being ruled out.
A separate meeting is due to be held this week between Southern and the drivers' union Aslef.
Aslef leaders have recommended two proposed agreements to resolve the dispute in recent months, but both were rejected by drivers. There is little sign of any progress being made between Southern and the two unions in previous talks.
Southern's 300,000 passengers have endured a year of disruption because of the strikes and other problems such as staff shortages.
Labour's manifesto, due to be published in the coming days, will include a pledge to take rail franchises back into public ownership when they run out.
The policy will help keep the Southern dispute in the spotlight before polling day on June 8.