A planned 24-hour strike on London Underground's Piccadilly Line on Wednesday has been called off.
The 24-hour walkout will still go ahead on the Central and Waterloo & City lines, the RMT union said.
The union said it was suspending the action after progress was made in talks in a dispute over industrial relations.
Members of the drivers' union Aslef will also be on strike on Wednesday on the Central Line - the second busiest on the network.
RMT general secretary Mick Cash praised the RMT members on the Piccadilly Line "whose solidarity and resilience has been the decisive factor in forcing London Underground back to the negotiating table".
But he said there was "a growing culture on London Underground that revolves around refusing to employ enough drivers, bullying staff and expecting our members to pick up the pieces when the service breaks down".
"As a result of that management side failure, the action on the Central Line goes ahead as planned," he added.