Washington (CNN) All seven Democratic presidential candidates who met the qualifications to participate in next week's debate declared their support on Friday for a local labor union and said they would not participate in the debate if they have to cross the union's picket line.

UNITE HERE Local 11 sent a letter Friday to all the Democratic presidential campaigns informing them of a labor dispute involving their union on Loyola Marymount University's campus, the site for next week's debate. LMU subcontracts its food service operations to a company called Sodexo, and Local 11 has been in negotiations with Sodexo since March for a collective bargaining agreement, according to the letter. A resolution has not been reached and Sodexo last week canceled scheduled contract negotiations, according to the union.

After receiving the letter, the candidates -- Elizabeth Warren, Bernie Sanders, Andrew Yang, Joe Biden, Pete Buttigieg, Tom Steyer and Amy Klobuchar -- all announced their support of the union.

A spokesperson for the DNC, Xochitl Hinojosa, said the DNC and LMU learned about the labor dispute on Friday.

"While LMU is not a party to the negotiations between Sodexo and Unite Here Local 11, (DNC chairman) Tom Perez would absolutely not cross a picket line and would never expect our candidates to either. We are working with all stakeholders to find an acceptable resolution that meets their needs and is consistent with our values and will enable us to proceed as scheduled with next week's debate," Hinojosa said in a statement.

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