Prime Minister David Cameron is to renew his vow to boost NHS funding and create a "seven-day" health service in his first major post-election speech.
He will commit to a pre-election pledge to increase budgets by at least £8bn a year by 2020, during his speech at a GP surgery in the West Midlands.
Outlining the government plans, he will say the NHS is "safe in our hands".
But doctors' representatives said without detail the announcement was "empty headline-grabbing".
The British Medical Association said the government was yet to explain how it would deliver additional care at a time of "chronic" doctor shortages.
Before the election, the Conservatives gave their backing to a plan by NHS England chief executive Simon Stevens to fill a funding gap estimated at £30bn a year by 2020.
This aims to make £22bn in efficiency savings, with the rest coming from taxpayers.
Labour said before the poll that Tory plans for "extreme" spending cuts threatened the NHS.
BBC health editor Hugh Pym said Mr Cameron had chosen the issue for his first major speech since the election to show "there is a real commitment to deliver" a seven-day NHS.
Mr Cameron is expected to describe the health service as the embodiment of "one nation" politics.
He will say the proposals will transform services across the country, with more GPs, faster access to new drugs and treatments.
They will also bring a greater focus on mental health and healthy living, he will say.
The PM is expected to say it is "shocking" how death rates for patients admitted to hospital on a Sunday are up to 16% higher than those admitted on a Wednesday and that a seven-day service would help save lives
"Our commitment to free healthcare for everyone - wherever you are and whenever you need it," he will say.
"So I believe that together - by sticking to the plan - we can become the first country in the world to deliver a truly seven-day NHS."
The government is promising better access to doctors and healthcare
This must be done to preserve the values of the NHS that are "so central to our national identity", Mr Cameron will add.
"To keep our people healthy, to look after them when they fall ill, to care for the elderly with dignity and to ensure that free healthcare is always there whenever people need it most."
Mr Cameron is expected to deny that staff will have to work longer hours.
He will argue instead that work patterns must be more flexible, to ensure doctors and nurses are available at the right times.
But the Royal College of Nursing warned any cuts in pay associated with delivering a "seven-day" health service could lead to industrial action.
Its general secretary Peter Carter told the Independent there was a "very modest higher level of remuneration" for working unsocial hours, including over weekends and holiday periods.
Any changes to that would be "strongly resisted", he said, adding: "Any attack on that and I do fear it would result in industrial action."
Health Secretary Jeremy Hunt said the body was "really jumping the gun".
"We haven't made any proposals whatsoever about changing nurses terms and conditions," he said.
Dr Mark Porter, British Medical Association council chairman, said the government needed to clarify how it intended to "translate this announcement into reality".
"The real question for the government is how they plan to deliver additional care when the NHS is facing a funding gap of £30bn and there is a chronic shortage of GPs and hospital doctors, especially in acute and emergency medicine, where access to 24-hour care is vital," he said.
"Without the answer to these questions this announcement is empty headline-grabbing and shows that even after polling day, politicians are still avoiding the difficult questions and continuing to play games with the NHS."
Prof Chris Ham, chief executive of the King's Fund charity, said a seven-day NHS was "absolutely the right thing to do" but that money was "the key question".
He told Radio 4's Today programme the £8bn pledge is "to be welcomed, but that will really help to keep existing services running, it won't fund all the new commitments we've heard of during the election campaign including seven-day working".
He also said there was "real workforce shortage" in some fields, with hospitals "already struggling to recruit enough senior medical staff".
Downing Street said the GP Access Fund, set up under the previous Conservative and Liberal Democrat coalition government, was already extending opening hours.
Andy Burnham, Labour's shadow health secretary, said pre-election that Tory plans were not credible without investment in extra NHS staff.
"With the NHS in increasing financial distress, David Cameron must set out clearly how it will be paid for," he said.