Prime Minister David Cameron refused to budge over an across-the-board 1% pay rise for all NHS workers, as strike action looms.
Speaking on LBC radio, the PM insisted it was a choice between pay for staff, or treatments for patients.
Paramedics are set to walk out for 24 hours on Thursday, with another day of strike action is planned for February.
Unions said they had no option but to take action after the government refused to implement the recommendations of an independent pay review bo
Staff have been offered a 1% rise but this has been restricted to those not already receiving an incremental increase. The NHS pay review body said the rise should be given to all staff.
Apparently paving the way for the walkout, Cameron said: "We've said there are constraints and the more we spend on pay, the less we're able to sustain levels of doctors and nurses. The offer is everyone gets one per cent, but not in addition to other incremental pay increases.
"We need to keep the pay bill under control because we've put more money into the NHS, but if you put more in to pay then you leave less for patients. We had to make this difficult condition but it's about controlling the pay bill. People do understand that if we had accepted pay recommendation in full, it would have meant millions going to pay, not treatments."
The walkout by members of Unison, Unite and the GMB unions may involve up to 500,000 staff.
A spokesman for Unison said: "Strike action is always a last resort and the health unions have been asking for a meeting with the Health Secretary to resolve the dispute for months."