Coronavirus cases in one part of Wales are increasing at an “alarming rate”, a health board has said.
Aneurin Bevan health board said its hospitals were under “significant” pressure due to Covid patient numbers.
It had already announced it would be halting outpatient appointments and non-urgent planned surgery from Monday.
The stark warning comes as First Minister Mark Drakeford said Wales’ NHS was in danger of becoming the “national coronavirus service”.
On Saturday, the day the number of positive Covid-19 tests passed 100,000 in Wales, the family of Ted Edwards, 73, from Monmouthshire, said they were “really concerned” after he spent more than 19 hours in an ambulance outside the Grange University Hospital in Cwmbran.
The Welsh Ambulance Service said it was “facing high demand” across the country “with acute pressure” around the hospital leading to “some long delays with patients on our ambulances”.
The health board said: “The number of Covid positive patients in our communities is increasing at an alarming rate and we need everyone to play their part to ensure our services are available for when our sickest patients need them.”
Weekly infection rates across the five south Wales counties the health board covers averaged about 550 cases for every 100,000 people.
Speaking about the threat faced by the NHS, Mr Drakeford said unless “we take all the action we can [not just] as a government, but as a population”, even more restrictions would be “unavoidable”.
“The huge danger here is that we transform our National Health Service into a national coronavirus service.
“If the numbers continue to go up as they are, then we will end up diverting our staff resources away from all the things that we expect and need them to do, simply to take care of an ever-rising number of people who are so ill with this dreadful disease that they have to be looked after in hospital.
“We need our health service to be able to respond to all those other things that happen in people’s lives in Wales.
“If the numbers continue to escalate in the way they are then, even more restrictions straight after Christmas seem to me to be unavoidable,” he told BBC Radio Wales’ Sunday Supplement.
He has previously said the coronavirus situation was “very difficult” but not out of control.
Last month, a senior doctor said in an email, seen by BBC Wales, that she had “huge concerns” about patient safety ahead of the Grange hospital opening four months ahead of schedule.
But Mr Drakeford told BBC Politics Wales “it was the right thing to open a hospital that was ready to open”.
“Imagine what it would be like in Aneurin Bevan [health board area] if we didn’t have all the beds that are available today in the Grange hospital in addition to what is available,” he added.