The East of England Ambulance Service says it is on the brink of declaring a major incident.
Patients have been urged to only call 999 for an ambulance for “life-threatening illnesses or injuries” as it warned the NHS it is on “standby” to declare a major incident.
The service - which covers Hertfordshire, Bedfordshire, Essex, Cambridgeshire, Norfolk and Suffolk - has been under extreme pressure since July.
But within the last few days some of its hospitals had ambulances queuing to drop off patients.
An East of England Ambulance Service spokesperson said: "The NHS is currently facing incredibly high demand and we are working very closely with our partners to speed up handover delays at hospitals to improve care for our patients.
"We experienced increased pressure across the eastern region over the weekend caused by lengthy handover delays at hospitals and 999 demand.
"We moved to major incident standby on Saturday night and have remained at that level of escalation to enable us to better direct our resources to focus on patient care."
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