San Francisco has become the first city in the U.S. to require businesses to provide fully paid time off for new parents.

The city’s board of supervisors on Tuesday unanimously passed the new law, which mandates that all companies with more than 20 employees pay 45% of a worker’s regular salary for up to six weeks of parental leave following a birth or adoption. The state of California currently pays the remaining 55 percent.

“Our country’s parental leave policies are woefully behind the rest of the world, and today San Francisco has taken the lead in pushing for better family leave policies for our workers,” said Supervisor Scott Wiener, who sponsored the legislation, in a statement. “We shouldn’t be forcing new mothers and fathers to choose between spending precious bonding time with their children and putting food on the table.”

The law will apply to mothers and fathers who work at least eight hours a week. It will take effect in 2017 for companies with more than 50 employees, and in 2018 will extend to companies with more than 20 workers.

The law will get another procedural vote next week and needs approval from Mayor Ed Lee before becoming official, but the unanimous vote makes it veto-proof.

The U.S. lags behind most of the rest of the world in granting paid parental leave. Federal law allows up to 12 weeks of unpaid leave, and California, New Jersey and Rhode Island provide partial pay.

The legislation was bitterly opposed by small businesses, who say they will be unfairly burdened.

“This is one more thing that puts San Francisco businesses at a disadvantage to their regional counterparts,” Mark Dwight, president of the city’s Small Business Commission told the San Francisco Chronicle before the supervisors’ vote. “If we want all our small businesses to move out of our city, then we’re doing the right thing.”

Businesses may end up paying less -- pending legislation in Sacramento would boost the state’s share of paying parental leave to 70%.

Income inequality and better pay have become hot-button issues in San Francisco, as the tech-fuelled housing boom has made living in the city unaffordable for many. City restaurants are already required to add a “Healthy San Francisco” fee to help pay for employees’ medical coverage, and last week, California signed into law the nation’s highest minimum wage, $15 an hour starting in 2022.