The expected reopening of the historic Tyne Pedestrian and Cyclist Tunnels between Jarrow and Howdon has been pushed back to Autumn 2018.
Engineering conditions and contractual problems have continued to affect progress on their refurbishment.
The expected date was confirmed at the meeting of the NECA (North East Combined Authority) Transport North East (Tyne and Wear) Sub-committee on Friday 23 February.
NECA is the seven councils which serve County Durham, Gateshead, Newcastle, North Tyneside, Northumberland, South Tyneside and Sunderland.
Transport sub-committee chair, Cllr John Harrison said: “I know this news will be a disappointment to pedestrians and cyclists who regularly need to cross the river between Jarrow and Howdon.
“The project has continued to suffer setbacks. Many of the engineering problems we have encountered could not have been known at the outset.
“The tunnels are an extremely difficult and challenging environment and the work is incredibly complex. It was only when we stripped the tunnels back to their original shells that we could fully quantify the extent of corrosion, contamination and water ingress.
“Issues with a key sub-contractor have also added to delays.
“One of our key aims before the project started was to use this once-in-a-generation opportunity to address issues whenever we encountered them. Otherwise we would have had to keep going back year after year, leading to partial closures and continued disruption.
“We are committed to opening the historic tunnels as soon as it possible as we know how important the tunnels are to the communities on both sides of the river.”
The Grade-II listed tunnels were closed in May 2013.
The free-to-use replacement shuttle bus service for up to 24 passengers and 16 bicycles and a Night Service for shift workers will continue.