Hospitals across England have been told to cancel non-emergency operations in the new year to prepare for a post-Christmas surge in patients.
The first weeks of January are often the busiest of the year with winter illnesses peaking, combined with the growing day-to-day demand in A&E.
So an emergency panel of NHS bosses is urging hospitals to cut back on their routine work, such as knee and hip ops.
They hope it will give hospitals some breathing space to cope.
Publicly, no figure is being put on the number of operations that should be put off, although the BBC understands hospitals are working on the basis of doing 10% fewer.
That would mean in the region of 15,000 operations not taking place in the first two weeks of January.
The panel has suggested hospitals use the staff freed up by the move to set up "hot clinics" staffed by experts in conditions such as respiratory illness to take the pressure off A&E.
The directive is the first to be issued by the NHS National Emergency Pressures Panel, a new group of senior doctors, nurses and managers set up to advise NHS England.
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Panel chair Prof Sir Bruce Keogh said it would be sensible for hospitals to curtail the amount of planned work they are doing until at least mid January.
"NHS staff are working flat out to cope with seasonal pressures and ensure patients receive the best possible care.
"However, given the scale of the challenge, hospitals should be planning for a surge that comes in the new year by freeing up beds and staff where they can to care for our sickest patients."
He said this would reduce the need for last-minute cancellations which were unfair on patients.
It comes as figures released on Thursday showed pressures had already started building.
The weekly bulletin from NHS England showed over 1,000 beds were closed because of the vomiting bug Norovirus - nearly 10% of the hospital bed-stock - while ambulances were increasingly likely to find themselves delayed when they dropped off patients at A&E.
Pauline Philip, the NHS national director for emergency care, said it was a sensible move.
She also urged hospitals to make the most of the extra £350m winter funding provided by the government, which was released into the system last week.
And she added: "There is still time for the public to play their part by ensuring they have their flu jab and by using local pharmacies and NHS 111."
Prof Derek Alderson, president of the Royal College of Surgeons, welcomed the move as it provided clarity over what should be done as pressures grow.
But he said it was still pretty "short notice" for those patients who face having their operations cancelled.
And he urged hospitals to prioritise cancer treatment and other planned operations that, if cancelled, would harm patients.