Hospitals could be stripped of services in the run up to the next general election, the new NHS chief says.
The NHS deficit topped £500m last year
In his first interview since becoming NHS chief executive earlier this month, David Nicholson said there would be up to 60 reviews of hospitals in England.
He said the changes could affect every region, and may lead to emergency, maternity and paediatric care being centralised in fewer hospitals.
Mr Nicholson told The Guardian the NHS was facing some "tough decisions".
It comes after the BBC last month identified several trusts in London, Surrey, Sussex, Cornwall and Lancashire which were considering down-scaling or even closing major hospitals.
Mr Nicholson, who has worked in the NHS for 29 years, said some of the changes would be aimed at reducing the NHS deficit, which topped £500 million last year.
But he added it was also about improving services by providing the best care in fewer centres, although he acknowledged this would mean patients travelling further for treatment.
"Undoubtedly there will be tough decisions to make over the next 12 months to reflect changing services.
"Some will come sooner (than the general election). We are going to have to tackle the big patient issues.
"I understand the politics of it, but this is about the way we deliver care which is predominantly closer to home."
MPs are known to be touchy about the prospect centralising services even if they support the policy on a national level because of the public's affection for their local hospitals.
Labour lost a parliamentary seat at the 2001 election when Richard Taylor ran as an independent protesting about the removal of the A&E department at Kidderminster hospital.
Liberal Democrat health spokesman Steve Webb said: "It is vital that any changes to the delivery of health services are driven by clinical priorities, not financial crises.
"The public is entitled to be sceptical when big changes to local hospitals happen at a time of financial pressure but are presented as being solely about patient care.
"Communities facing hospitals closures will be asking why these 'reconfigurations' are being made at a time of severe cost-cutting."
And shadow health secretary Andrew Lansley said: "The Chief Executive's first message should be one of hope and opportunity but it is one of closures and cuts.
"He said that he understood the politics of the NHS but it is more important for him to understand the service requirements."