Tim Byles, the chief executive of Partnerships for Schools, the organisation charged with delivering the pound;45 billion flagship initiative, has admitted that the original targets were unworkable.
He said: "Everyone across government accepts that the early targets were not based on any experience and were not realistic. We will reset the baseline this year so we have realistic objectives. We are in discussions with ministers at the moment about the time frame."
Mr Byles said some local authorities would still miss even the extended deadline, but added that lessons had been learned from early mistakes in the programme.
"The authorities that were chosen first were those with the greatest needs and some of those have found it difficult to deliver," he said. "I'm not surprised by that.
"But we are significantly reducing the problems and I am confident that we can deliver."
Wave four of the programme was announced in December. All authorities now receiving funding have to prove they are ready to make immediate progress, alongside other initiatives designed to keep projects on track.
Mr Byles repeated concerns of officials at the Department for Education and Skills that there is a lack of expertise to manage such a large project. He said London boroughs may have to consider joining forces to share resources.