NEW YORK/SAN FRANCISCO (Reuters) -Amazon.com workers at seven U.S. facilities walked off the job early on Thursday during the holiday shopping rush as workers protest what they say is the retailing giant's unfair treatment of its employees.

Warehouse workers in cities including New York, Atlanta and San Francisco were taking part in what Teamsters officials called the largest-ever strike against Amazon - but which may cause barely a ripple in the company's extensive shipping operations.

As the world's second-largest private employer after Walmart, Amazon has long been a target for unions that say the company's emphasis on ever-faster speed and efficiency can lead to injuries. The company says it pays industry-leading wages and uses automation designed to reduce repetitive stress.

Amazon shares were up 1.8% on Thursday afternoon.

Workers told Reuters they want Amazon to come to the bargaining table and recognize the pressure to meet demands that affect their health. However, the strikers represent a small number of the 800,000-plus people employed by Amazon at more than 600 U.S. fulfillment centers, delivery stations and same-day facilities.

"(Amazon) pretends there isn't a quota system, but there's a rigorous quota system that pushes people beyond their real physical limits in an unnatural way," said Jordan Soreff, 63, who delivers about 300 packages a day for Amazon in the New York City boroughs of Queens and Brooklyn. "The more you do, the more you're expected to do."

Soreff was one of about 100 people outside the Amazon facility in Queens, including many Teamsters members who do not work for Amazon. However, the facility was continuing to operate, with other drivers going in to work and then leaving in trucks, assisted by police, who were stopping protesters from blocking the drivers.

The Teamsters have "intentionally misled the public" and "threatened, intimidated and attempted to coerce" employees and third-party drivers to join them, an Amazon spokesperson said.

Amazon has multiple locations in many U.S. metropolitan areas, shielding it from potential disruptions. The company has said it does not expect any effect on operations during one of the busiest times of the year. In 2023, the company sold more than 500 million items from independent sellers on Black Friday and Cyber Monday.

"It is possible there may be some isolated incidents of delay, I just do not think there will be a material impact," said Morningstar analyst Dan Romanoff.

Earlier this year, Amazon announced a $2.1 billion investment to raise pay for fulfillment and transportation employees in the United States, increasing base wages for employees by at least $1.50 to around $22 per hour.

The International Brotherhood of Teamsters had given Amazon a deadline of Dec. 15 to begin negotiations - but that day passed without talks. The Teamsters say they represent 10,000 workers at 10 Amazon facilities, but the e-commerce giant disputes this, saying there have been no elections or bargaining orders for the locations.

RESISTANT TO UNIONS

Labor actions have picked up pace across service industries following a period when workers at manufacturers in the automotive, aerospace and rail industries won substantial concessions from employers. U.S. port workers are due to potentially strike in mid-January if contract talks are not resolved.

A union representing more than 10,000 Starbucks baristas authorized a potential strike earlier this week, after strikes roiled companies including planemaker Boeing earlier this year.

Amazon has still not recognized the first-ever facility to vote to unionize in Staten Island, and has filed objections with the National Labor Relations Board over that 2022 union vote. In a federal lawsuit filed in September, Amazon challenged the constitutionality of the NLRB, formed during the Great Depression of the 1930s.

In San Francisco, there were at least three dozen protesters at the Amazon facility, with a Teamsters organizer estimating that between 15 and 20 were warehouse employees.

Janeé Roberts, a 30-year-old San Francisco resident who has worked at the facility for almost two years, said her main reason for supporting the strike was safety conditions.

"Not only do I look at my coworkers and see how dog-tired and wear and tear it takes on their bodies, but we're not even given proper benefits as part-timers," Roberts said while holding a sign outside the gates.

Amazon, whose businesses include grocery chain Whole Foods, will face other union actions in the months ahead. Workers at a Philadelphia Whole Foods in November filed to hold a union election, the first since Amazon acquired the business in 2017.

Germany's United Services Union also announced strikes at Amazon warehouses across the country in solidarity with Teamsters, starting on Thursday.