WELLINGTON, New Zealand — New Zealand’s government said on Monday that it would try to pass a law decriminalizing abortion, taking on an issue that the nation’s lawmakers have long avoided even as the country built a socially liberal reputation on the world stage.

Under current law, women seeking an abortion must claim that the pregnancy would harm their physical or mental health, and have the procedure approved by two doctors.

The government’s proposal would eliminate those requirements for women who are up to 20 weeks pregnant and remove abortion from a 1960s Crimes Act. Women who are more than 20 weeks pregnant would legally be able to have an abortion if a doctor approved it.

“The purpose is to modernize our law and ensure that abortion is treated as a health issue,” Andrew Little, the justice minister, told reporters in the capital, Wellington. He added that the changes would bring New Zealand into line with “many other developed countries.”