Network Rail (NR) has announced plans to sell £1.8 billion of its "non-core assets" to meet the increased costs of major infrastructure projects.
The organisation's chairman, Sir Peter Hendy, claimed "the bulk" of its upgrade plans will go ahead, although some will be completed later than originally scheduled.
He announced the plan to sell assets in a review into NR's £12.5 billion enhancement plan for 2014-19, which he found was "undeliverable".
Electrification of the Midland Mainline from Sheffield to Bedford is now not set for completion until 2023, with the TransPennine line between Manchester and York by 2022.
It emerged last month that the cost of electrification of the Great Western line between London and south Wales could rise to £2.8 billion, despite an estimate of £1.6 billion being given last year.
Sir Peter said: "Working closely with the Department for Transport (DfT) we have ensured that no infrastructure project has been cancelled and the bulk of the investment programme will be delivered by March 2019.
"Some projects will cost more and take longer than originally expected, but we will see the job through to deliver better journeys for passengers. My review has clearly found that the original plan was unrealistic and undeliverable.
"This new railway upgrade plan is a more robust and deliverable plan but it is not without its own risks and challenges which Network Rail will work tirelessly to address."
NR became a public body last year, which meant it could no longer borrow money privately to fund enhancements, and had to rely on the Government.
Sir Peter said that the DfT has agreed to increase its borrowing limit by £700 million.
NR's saleable assets could include unused depots, land under railway arches and retail space inside stations.
Meanwhile, a separate review by Dame Colette Bowe into what lessons can be learned from the failure in rail investment planning found that too much responsibility was attributed to the Office of Rail and Road (ORR), whose role "was unclear".
She wrote: "It has become apparent to me in this review that parties to the planning process ascribed to the ORR functions it was not undertaking.
"The clearest example of this is the ORR's role in assuring affordability."
She found that the DfT expected the ORR to ensure the projects "could be delivered within the funding envelope", whereas the regulator states that it only assesses the affordability of financing costs.
Dame Colette added: "I conclude that the role of the regulator for future rail enhancement planning needs to be rethought."
Transport Secretary Patrick McLoughlin said that he accepted all of the report's recommendations and announced that the role and responsibilities of the ORR will be "fundamentally reviewed".
David Sidebottom, passenger director at the independent watchdog Transport Focus, said: "Passengers will be reassured that Sir Peter Hendy has found ways to continue with the investment in the much-welcomed and long-promised improvements.
"For passengers, this follows years of above-inflation fare increases, increasingly crowded trains and disruptive engineering works.
"However, there are delays to schemes and new plans to bring in revenue with the sale of station retail facilities.
"Passengers will want to see that these new plans are robust and can be now be delivered to help rebuild trust."
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