Hospitals in and around Paris have been told to reduce non-Covid treatments by 40%, as demand for intensive care beds (ICU) neared saturation point.
On Monday take up of ICU beds for Covid patients was just 83 short of the 1,050 capacity set aside for the region, reports the BBC.
France has tried to speed up its slow vaccination campaign but remains dogged by high infection rates.
It has tried to avoid major lockdowns and its health director said on Tuesday one in Paris would be a "last resort".
Jerome Salomon told RTL radio on Tuesday this was "not on the agenda" but that the situation was being monitored "day by day".
The head of the Île de France, or greater Paris, region - France's most populous at 12 million - said on Monday that it was "very tense".
Aurelien Rousseau said "we needed to react very fast" in giving "a firm and immediate order" to cancel 40% of scheduled non-Covid hospital care.
This followed a net increase into intensive care of 35 patients per day over the past two weeks.
The latest move would boost intensive care bed capacity to 1,577 by next week.
Salomon on Tuesday admitted the situation was tense, but that beds were being freed up.
He added: "Lockdown is a last resort measure that would be submitted to the government and the president if we were under the impression the hospital system could not cope."