Suffolk leaders are calling for funds to be transferred "as soon as possible" so that work can begin on a promised rail upgrade.
Prime minister Rishi Sunak pledged rail improvements for East Anglia after he scrapped part of the HS2 railway line from Birmingham to Manchester after deciding it was too costly.
Among the works he committed to were two crucial upgrades for this region - one at Haughley Junction near Stowmarket and another involving a rebuild at Ely North Junction.
Now Suffolk Chamber, Suffolk County Council and Greater Anglia have written to transport secretary Mark Harper calling for the funds to be made available quickly - and for work on the much cheaper Haughley project to begin as soon as possible.
The work at Haughley is estimated at around £20m while the Ely scheme could be £500m or more.
Suffolk Chamber chief executive John Dugmore, county council leader Matthew Hicks and Greater Anglia managing director James Burles have written a joint letter to Mr Harper welcoming the commitment - and calling for speedy action.
They are asking for full development funds to be made available to Network Rail "as soon as possible", to allow them to reinstate the project team and the necessary resourcing.
Network Rail was "ready and able" to pull together a team to progress the full scheme design and begin the consent process, they said.
"We ask that Haughley Junction improvements be progressed as a quick and deliverable Phase 1 of the overall capacity enhancements," they said.
"This request reflects the smaller scale and cost of the project, shorter delivery timescales, and the opportunities for resource and disruption management by aligning work with planned track maintenance.
"Such news over the next few months, especially with this element of phasing in of elements of the overall project, would send a clear and demonstrable message of the seriousness of the intent of the government in investing in this project."
It would send out a "timely and welcome" message to local and regional businesses and residents, they said.
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