A four-day strike on the Docklands Light Railway (DLR) due to take place from Friday has been called off.
RMT union members were due to walkout at 04:00 BST in a dispute over working conditions.
The strike would have affected runners required to register at the ExCel centre in east London, which is on the DLR line, before Sunday's London Marathon.
RMT members voted to suspend the action after talks on Thursday.
The union's general secretary Mick Cash said: "After 13 days of intensive talks, RMT's negotiating team has been able to secure significant progress on the key issues of the threat to jobs and conditions from outsourcing and a range of grievances around the principles of workplace justice."
The Mayor of London, Sadiq Khan, announced that the planned action had been called off at 18:22 BST.
Mark Davis, interim general manager of the DLR, said: "For the thousands of runners raising millions of pounds for charity this weekend, we are delighted that the planned industrial action on the DLR has been suspended.
"Our services will help all those participating and supporting the London Marathon travel across London for this fantastic event."
However, people are being advised that from 06:00 BST on Sunday, there will be road closures in place along the Marathon route.
The proposed strike between DLR operators KeolisAmey Docklands Ltd (KAD) and RMT union was over the "fundamental issues" of workplace justice, fairness and the outsourcing of key functions.
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