LOS ANGELES  -- Los Angeles County is crafting a law to raise the minimum wage to $15 per hour over the next five years, with supporters arguing it will help lift the working poor into the middle class and opponents warning businesses will have to cut back, move out or close down.

With Tuesday's 3-2 vote by the Board of Supervisors, the nation's most populous county joins the list of communities that believe a wage floor will reduce poverty.

It's an argument that has gained traction amid concerns over the shrinking middle class and rising income inequality.

Democrats, including presidential front-runner Hillary Rodham Clinton, have said they support a higher federal minimum wage, which is currently $7.25 per hour.

Vice President Joe Biden was scheduled to promote a higher minimum wage during a stop Wednesday at a washroom equipment manufacturer in Los Angeles, which last month enacted a progressive minimum wage increase to $15 per hour.

Seattle and San Francisco are also gradually raising their minimum wage to $15 per hour.

The county supervisors directed lawyers to draft a similar pay scale that would top out in 2020, although smaller businesses would have an extra year to reach that mark. Beginning in 2022, the wage would be increased annually based on inflation.

The board is expected to pass the measure later this year.

The law would have a limited effect in a county of 10 million people since it would only apply to unincorporated areas - not its 88 cities - and a slice of county workers.

Rep. Janice Hahn, D-California, who applauded the vote, said it would affect more than 100,000 workers.

Before the vote, dozens of opponents representing restaurants, small businesses and trade groups and argued that higher wages would hurt the bottom line for businesses and might result in higher prices, reduced profits, workforce cuts or even closures.

Los Angeles Mayor Eric Garcetti was among those arguing for the increase.

"Poverty is very, very expensive," Garcetti said. "When we lose billions in lost wages, when we see folks who can't support themselves, who winds up paying for it? We do."

Supervisors repeated some of the same arguments before voting.

"We're not paying people to be in the working class anymore. They are now in the poverty class," Supervisor Sheila Kuehl said.

Supervisor Michael D. Antonovich said the law could push businesses, even big employers such as Wal-Mart or the Universal Studios theme park, into neighboring cities that lack minimum wage requirements.

"Are you going to have businesses stay here, thrive and create jobs or are you going to have another exodus?" Antonovich asked.

Associated Press Writer Christopher Weber contributed to this report.