Organizers say fast food restaurant workers in 100 U.S. cities, including Cleveland, will walk off the job Thursday, as part of a continuing push to raise wages above $15 an hour in the industry and secure the right to unionize.

IT'S famed as a land of opportunity where anyone willing to work hard can make dreams come true.

But inside America a war is being waged between a shrinking middle class and the wealthy 'one per cent' that employ them.

Overnight, thousands of workers walked off the job in McDonalds, Burger King and Wendy's among other outlets in 100 cities around the country, in protest at the $7.25 minimum wage which they say is impossible to live on.

It's the largest event yet in a movement that is gaining momentum, as workers vent their anger at the divide between the haves and have nots.

Darrien Walker works at a Michigan McDonald's for 40 hours a week earning just $7.45 an hour.

He joined the group fighting for the minimum wage to be increased to $15 an hour, to bring it into line with today's living standards.

"I would personally like to see a substantial increase in pay because even though the job is simple the fast food demand is higher than ever which can make things difficult. $7.40 is not enough," he said.

The campaign is being orchestrated by advocacy groups like Fast Food Forward and Low Pay is Not OK, along with traditional unions like Service Employees International, which represents more than 2 million people in the healthcare and cleaning industries.

Union President Mary Kay Henry said the goal is to change the conversation about what these jobs are worth.

"These are no longer jobs being done by teenagers who need extra money. These are jobs being done by adults that can't find any other work," she said.

So far, the groups have used social media to shame the corporate giants into action.

Low Pay is Not OK recently embarrassed McDonald's by lampooning a series of budgeting tips which assumed workers would have a second job, while another video took aim at their providing holiday tips like breaking your food into smaller pieces to make it last longer.

United States Studies Centre lecturer David Smith said the US has the lowest rates of social mobility in the OECD with the chances of making it increasingly slim.

"It's getting increasingly difficult to tell the middle class and lower class apart in the US. Employment is not only increasingly low wage, it's increasingly insecure as well," he said.

The $200 billion fast-food industry has become a major symbol of this inequality with insecure jobs that are becoming a career not just for teenagers part-time, but single mothers and older workers as well.

"The sheer number of adults in the industry has just exploded" because fast-food restaurants "not only survived, but thrived during the economic recession," Saru Jayaraman, director of the Food Labor Research Center at Berkeley, told Bloomberg.

In New York the number of fast-food workers has grown 10 times faster than private sector jobs, to more than 55,000 people since the year 2000, the New York Times reports.

However about 27 per cent of fast food workers across the country are on food stamps, compared to 15 per cent of other Americans, research from the University of Minnesota Population Center shows.

To make things worse, Mr Smith said the minimum wage has "hardly moved" in the last two decades, meaning life is becoming more difficult for those without a steady job.

"Someone who works in fast-food, they can't survive on a single fast food job. They have to be working multiple jobs."

"It's not just people we would consider poor, it's who used to make up the lower ranks of the middle class, it's getting a lot harder for them," he said.

Mr Smith said it's not just hospitality workers affected, with other middle class jobs like journalism and teaching hard to get a start in.

"A lot of businesses will have people doing unpaid internships for months and years before they get a shot. If you want entry to finance, law or journalism, you have to be wealthy enough in the first place to support long periods of non-payment," he said.

President Obama has called the gap between America's richest and poorest workers the "defining challenge of our time" and vowed to address the deficit between workers.

"The basic bargain at the heart of our economy has frayed," he said

"It should compel us to action. We're a better country than this."

But fast food giants like McDonald's, Burger King and Yum Brands say the don't control worker pay, which is often set by franchise agreements.

It remains to be seen whether the wage issue will become part of the wider political debate.

President Obama said he would back a Senate measure to raise the federal minimum wage to $10.10, more than a dollar higher than the $9 an hour rate he previously proposed.

Senate Majority Leader Harry Reid has promised a vote on the wage hike by the end of the year. But the measure is not expected to gain traction in the House, where Republican leaders oppose it.

In the meantime, Mr Smith said public walkouts are the best way of quickly drawing attention to the issue.

"So many Americans rich and poor alike eat fast food every day. It's a major part of fabric of American society so having a walk out is a major way of drawing attention to fact people who work are not able to survive on those jobs."

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