SHANGHAI  Thirty years after China began enforcing a one-child policy, this city is actively encouraging young couples to have a second child.

City officials are planning to visit homes, slip leaflets under doors and offer emotional counseling and financial incentives.

The world’s most populous country, it seems, wants to be a little bigger.

The new push, which aims to tackle growing worries about the country’s shrinking work force and aging population, is the most public effort yet to counter a policy that is considered both a tremendous success and a terrible failure. While it has kept population growth under control, it has also led to forced abortions.

China is not doing away with the one-child policy, which still largely applies to urban residents, but is allowing more exceptions to the rule. Shanghai, with 20 million residents one of China’s biggest cities, is leading the effort.