MOSCOW — A deeply unpopular government plan to raise retirement ages in Russia for the first time in 90 years has created an unusual schism within President Vladimir V. Putin’s typically monolithic ruling party.

The overhaul, which the government says is necessary to cope with a shrinking work force and a growing retiree population, has touched off street protests in more than 150 cities and divided the party, United Russia, usually known for its lock step unity.

The turbulence poses no serious threat to Mr. Putin, whose approval rating slipped in late June but has since begun to recover. Analysts say, however, that the plan tests how far Mr. Putin can go in tweaking the terms of an implicit bargain at the core of his rule: a surrender of political freedoms in exchange for economic stability and national pride.

Russians have among the earliest retirement ages in the world, unchanged since they were set by the Soviet Union in 1928, early in the rule of Joseph Stalin. Men qualify for pensions at 60 and women at 55, and in some industries and regions women can retire as young as 50.