The Government's NHS reforms are essential to avert a £20 billion funding shortfall by 2015, David Cameron has warned.
Signalling his determination to press ahead with the highly controversial changes, the Prime Minister insisted the status quo was "not an option".
Speaking to NHS staff at Ealing Hospital in west London he proclaimed his own "love" for the health service and declared that the reforms were in the "national interest". But he claimed that the rising costs associated with an ageing population and increasingly expensive treatments could not be ignored.
"If we stay as we are, the NHS will need £130 billion a year by 2015 - meaning a potential funding gap of £20 billion," he said.
He ruled out additional Government borrowing, or asking people to pay at the point of delivery, to fill the hole.
"There's only one option we've got, and that is to change and modernise the NHS, to make it more efficient and more effective, and above all, more focused on prevention, on health, not just sickness," he said. "We save the NHS by changing it. We risk its long-term future by resisting change now."
Mr Cameron refused to "pre-empt" the outcome of the listening exercise launched by ministers in the face of widespread opposition to the reforms last month. The NHS Future Forum, set up to oversee the process, will report recommendations at the beginning of June and the Government would respond later in the month, he said.
But he insisted the reforms would be "evolutionary, not revolutionary" and a "logical extension of tried-and-tested policies initiated by governments of all parties in recent years".
Critics warn that the changes open the health service to full-blown privatisation. Rachael Maskell, of the Unite union, said: "David Cameron in his speech today was long on rhetoric, but short of specifics. This was a PR exercise in verbal gymnastics due to the political pressures he is under, especially from his Liberal Democrat allies."
TUC general secretary Brendan Barber said: "The Government's plans to 'modernise' the NHS will cost billions at a time when hospitals are being expected to find substantial efficiency savings. The end result will be a worse service for patients as private sector firms, led by the huge multinational companies, rush in to secure the most profitable services for themselves."