Apart from the huge cost, there is little doubt the current system works well for many.

In France the poverty rate among those older than 65 is less than 5 percent, largely because of the pension system, while in the United States it approaches 20 percent, according to the Organization for Economic Cooperation and Development. In France, life expectancy is increasing, while in the United States it is diminishing in significant sectors of the population.

With public opinion behind the strikers, and the unions emboldened by their success, the margin for maneuvering by the government appears limited. Fifty-three percent backed the strikers in a poll published Sunday in Le Journal du Dimanche.

Mr. Macron’s political learning on the job has not helped. Even some of his own supporters are starting to get anxious.

“We absolutely must remove the uncertainties for the French, that this reform won’t have a negative impact on their pensions,” said Benoît Simian, a member of Parliament from Mr. Macron’s party who represents an area around Bordeaux.

The standoff, he said, “hurts the reformist capacity of the government, which is a necessity for our future. Clearly, this could put a wrench in our ability to reform.”

The lack of clarity over who, if anybody, will win and lose in the new pension system has opened a door for Mr. Macron’s hitherto weak political opposition and for the unions. Some analysts say private-sector workers will come out ahead. That prediction has enraged the public sector.