More than 2,200 nurses at the University of Chicago Medical Center are walking off the job Friday morning, after contract talks with the hospital broke down this week amid a dispute over staffing levels and pay raises. CBS Chicago reports the striking nurses said they're being forced to work long hours and cannot provide the proper care their patients need.

Hundreds of nurses – many in their uniforms, others in red T-shirts – began picketing outside the hospital at 7 a.m. as their one-day strike began, the station reported.

The nurses say they’d like to return to work tomorrow, but the hospital is bringing in replacement nurses. The replacements have to be guaranteed several days of works. That means the nurses on strike won’t be able to return to work until at least Wednesday. @cbschicago pic.twitter.com/Aq859UKMzt — Mugo Odigwe (@MugoOdigwe) September 20, 2019

The striking nurses said they're sending a message about patient safety. "We did not walk out on our patients. We walked out for safe staffing, which is for our patients," nurse Johnny Webb said.

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"Nurses are not just striking just to be striking. It is not something that anyone wants to do," registered nurse Denise Summers said.

Summers has worked as a nurse at the University of Chicago Medical Center for almost 10 years. She said change is drastically needed.

"Nurses are not able to take lunch. Many times we're not able to take breaks. We're penalized if we take sick time. And you get burned out," she said.

One of the sticking points in contract negotiations has been staffing. National Nurses United said the nurses have filed more than 1,700 complaints detailing staffing problems since January 2017.

The nurses said state law requires a one-to-four nurse to patient ratio, but they often have a one-to-six ratio in the emergency room.

"We also have nurses that are taking care of sicker patients, so they have one to four when maybe they should be one to three," Summers said.

The union also has said because the hospital is often short on nurses, they are often asked to work in departments where they have little to no experience.

"Our OR for the pediatric population, the nurses that come in on the weekend are either from our adult side or they're on call," she said.

National Nurses United said nurses who do have experience in that field are required to be on call for up to 24 hours a week.

However, the hospital has said staffing is not an issue, arguing their staffing levels are the best in the state and city. The hospital says the number of staffing complaints from nurses represent less than half a percent of all staffing assignments during that time.

The hospital accused the union of distorting the facts on staffing issues.

"Unfortunately, as we really made a generous proposal around that, recognized as a generous proposal by the union negotiator, she put additional things on the table as core issues, and it was clear that we're so far apart on those that both sides determined there was no more productive conversation to be had," University of Chicago Medicine senior vice president Debi Albert said.

Albert said the main additional issue is compensation. According to the hospital, nurses represented by the union are already the highest paid in Chicago and Illinois.

Summers said the strike ultimately comes down to patient care, and getting hospital leaders to listen.

"We are there. We are at the bedside. We're in the clinics. We're in the procedure areas," she said.

Although the nurses will be on strike only one day, the hospital has said they won't be allowed back to work for five days.

To keep the hospital running during the strike, the University of Chicago Medical Center brought in hundreds of temporary nurses, and officials said they had to give them a five-day guarantee, so the striking nurses won't be back at work until Wednesday, when contract negotiations resume.

The walkout in Chicago comes on the same day that registered nurses staged a one-day strike against Tenet Health hospitals in Florida, California and Arizona on Friday. The Associated Press reports that about 6,500 National Nurses United members walked out at 12 Tenet facilities nurses, demanding better working conditions and higher wages.