It will take months before the NHS can fully restart services in the face of the coronavirus crisis, health charities and NHS providers have warned.
In a joint submission to the Commons Health and Social Care Committee, the Health Foundation, the King's Fund and Nuffield Trust said the impact of the pandemic on already exhausted health service staff should not be underestimated.
And a separate report from NHS Providers, which represents NHS organisations, warned there are challenges to ramping up care for people with non-COVID conditions while still caring for COVID patients.
Before the outbreak, the waiting list for planned treatment stood at around 4.4 million, but is expected to be much higher when the latest figures are published later today.
The charities' committee submission said the pandemic has exposed "pre-existing weaknesses", most obviously a long-term under-investment in health and care services and a "precarious" social care system.
It warned that an information campaign will be needed to urge the public to overcome their fears and start using the NHS again, while preparations must also be made for a possible second peak of COVID-19 alongside the usual winter pressures such as seasonal flu.
The organisations also said more personal protective equipment (PPE) will be needed as non-COVID services resume, more space must be allocated so patients and staff can socially distance, and there is a need for greater levels of testing.
"These issues will still need to be tackled alongside the backlog of demand," they said.
Nigel Edwards, chief executive of Nuffield Trust, said: "With the virus still at large there is no easy route back to the way things were before in the NHS, and unfortunately that means people waiting much longer and some services being put on hold.
"Hospitals and a whole range of services provided in the community will have to be remodelled to control infection and keep people safe, by separating out coronavirus patients and testing constantly and quickly at every level.
"We must be honest that this will slow things down."
Richard Murray, chief executive of the King's Fund, said: "All aspects of the health and care system will need to be back up and running if services are to return to any semblance of normality.
"In the case of social care, normality should not be the aim. The sector needs increased funding and fundamental reform."
For NHS Providers, Chief Executive, Chris Hopson, echoed some of the charities' concerns.
"The NHS has performed extremely well through the first peak of the virus, but that's just the first few laps of what we know will be a marathon," he said.
"Only now is the scale of the challenge for the rest of the race coming into view.
"Trusts will do all they can to restart services as quickly as possible.
"They'll seek to solve every problem they encounter as they've consistently done so far.
"They will build on the innovations they've developed over the last two months, like the 6,000 patient consultations a day now being delivered online, compared to 200 before the crisis.
"But one key lesson from the pandemic so far is not to over-promise.
"We must recognise that the NHS cannot deliver all that is now being asked of it. Expectations are already way ahead of reality."