Philadelphia officials on Monday flashed the green light for a bill that would allow the city's police department to stop arresting people who possess small amounts of marijuana.

Philadelphia would become the largest U.S. city to decriminalize marijuana possession.

The original bill passed city council in June with a veto-proof majority, but it was not until Monday that Mayor Michael Nutter agreed to sign the measure.

The bill's sponsor, Councilman Jim Kenney, says the bill calls for a $25 fine for people caught with less than 30 grams of pot, or just over an ounce. He says the offense wouldn't go on the person's record and compared it to a parking ticket.

Part of the compromise with the mayor is the addition of a $100 fine or community service for public consumption of marijuana. The city law is expected to take effect on Oct. 20. Under state law, though, possession remains a criminal offense.

A survey conducted by Connecticut’s Quinnipiac University in March found that 85 percent of Pennsylvanians favored the legislation.

Kenney had argued that arrests for pot possession unfairly targeted blacks. Of the 4,614 arrests Philadelphia police made for small amounts of marijuana in 2013, 83 percent were African-American, according to local media, even though studies show the number of black and white Americans who consume pot is roughly the same.

Nutter has faced mounting pressure from local black and youth organizations to sign the bill into law.

Al Jazeera and wire services