The timetable for implementing reforms of the NHS is "ambitious" but not unachievable, the Health Secretary will say.
Andrew Lansley has come under fire over the speed of his proposals, which will see GPs take control of the NHS budget from 2013 and NHS trusts, which manage the cash at the moment, will be abolished.
Mr Lansley will seek to reassure doctors attending a Royal College of GPs (RCGP) conference in Harrogate, promising full support for their new role.
He will accuse the previous Labour government of having "dithered and delayed in its approach to NHS reform".
Labour's approach "fell apart entirely" in the last three years due to a lack of clarity about what ministers were trying to achieve, he is expected to say.
"As a Government, we will not repeat these mistakes. That is why I have been so clear about setting out our ambitions for the NHS, the reforms we will make to achieve these ambitions, and by when we will make the reforms.
"It is true that the timetable is ambitious, but it is not a timetable which is unachievable.
"With two-and-a-half years with which to learn from pathfinder commissioning consortia and establish shadow arrangements, there is ample time for practices that do not yet feel ready, to secure capability collectively.
"These reforms give GPs the overall responsibility for the design of services, which meet their patients' needs, and facilitate a quick response when failures in those services arise."
He will tell GPs he does not intend to burden them with paperwork or involve them in the "minutiae of administration". Support will be available from health trusts, local authorities or "external partners".