Workers on Southern Railway are to stage a fresh 24-hour strike on April 4 in the row over staffing and the role of conductors, the RMT union said.
The union said it would reconsider action if Southern agreed to "firm date for talks over the future role of the guard."
A series of strikes on Southern over the past year has left passengers enduring long delays and cancellations.
Earlier this week tens of thousands of commuters struggled to get to and from work as three rail companies went on strike.
The announcement was made as members of the drivers' union Aslef started voting on a deal aimed at resolving their dispute over driver-only trains.
A Southern spokesman said: "We've not received any correspondence from the RMT on this matter. When we do we'll review it and respond. "In the meantime, they have announced a new strike date and we'll plan accordingly if it goes ahead.
"We've been able to run over 90% of our trains for our passengers on recent RMT strike days and we will plan to run a comprehensive service again."
The new strike coincides with a home game by Championship football club Brighton. Many fans travel to the ground on Southern services.