The NHS in Wales is entering its "most challenging period" as it deals with the coronavirus pandemic and rising waiting lists, its chief executive has said.
Dr Andrew Goodall said the health service is treating people for Covid-19 but also dealing with other emergencies and routine appointments.
There are now record waiting times in Wales for treatments to begin with more than 600,000 on lists.
Accident and emergency units are also under pressure, and the Welsh Ambulance Service has had to call in support from the military for the third time since the pandemic began.
It comes as the Welsh Secretary said the military can not be depended on to "rescue" the ambulance service in times of need.
Simon Hart told The Telegraph that the Welsh government had to understand that the military was not an “open-ended” resource to ease problems.
Dr Goodall told BBC Radio 4's Today programme: "I think it will be right to say that this feels like this is the most challenging period of time.
"We are still responding to a coronavirus context, we still have significant numbers in our system, we have high community prevalence levels, and, whilst the number of patients being hospitalised are much lower than we've seen over the last 20 months or so, it still means that we have patients who are affected by lots of the precautions that we take within our hospital and our healthcare environments."
"But the real thing that has changed over these last three or four months, in particular, is the recovery of activity because NHS staff want to ensure that patients are cared for and treated."
"We've actually seen months where high, if not record, numbers of patients are coming into our system from ambulances through to A&E, and of course we've been wanting to restore planned operations across the system."
"The numbers are increasing and we are probably at the fullest that we've seen across our system in the last 20 months at this stage."
"But we need to continue to make sure that we're also able to bring in patients who have been waiting for access to care over the last 20 months."
The First Minister said the ambulance service in Wales is operating under "enormous pressure" as a result of the growing number of people needing the service, as well as the necessity for paramedics to work under Covid-compliant restrictions.
Mark Drakeford MS told Sky News: "We've been able to secure some assistance from the armed forces and we're really grateful for that."
"We've had it throughout the pandemic. They (service personnel) won't be responding to emergency calls but they will be helping with some of the more routine work that the ambulance service does, freeing up trained ambulance personnel to deal with the most urgent work that the service has to provide."
In August just 68.7% of patients spent less than four hours in an A&E department before being admitted, transferred or discharged - well below the 95% target. And nearly 8,000 people had to wait longer than 12 hours.
Last month, the Welsh Government rejected calls from the Conservatives to declare an emergency in the ambulance service due to increasing demand and rising waiting times.
However, a new report revealed that ambulance crews are facing long delays stuck outside hospitals waiting for patients to be admitted.
Healthcare Inspectorate Wales said crews had to wait more than an hour to transfer a patient on 32,699 occasions - with around half of the patients being over the age of 65.
Dr Goodall was asked why patients can wait longer for a routine procedure in Wales than they do for the same surgery in England.
"We've have been affected by the decisions that we took back in spring 2020 to step away and ensure that the NHS was prepared," he said.
"Our waiting list has been increasing probably around 3% a month at this stage. They are similar increases that have been seen in the English system."
"Before coming into the pandemic we had some issues around our waiting times, and we've been focusing on actions to improve that and there has been very significant investment."
"As we have come out of the pandemic we have been really clear that, if we look at the numbers that we are facing at the moment, it could take the whole of a government term actually to clear those areas."