In a bid for increased year-round health care benefits, thousands of workers have gone on strike at 25 downtown hotels, dealing a potential blow to downtown business as the summer travel season winds down.

Housekeepers, servers, cooks and doormen hit the picket line early Friday at a list of swanky hotels including the Hyatt Regency, JW Marriott and the Sheraton Grand Chicago — and five more hotels could join the work stoppage “at any moment,” a spokeswoman for Unite Here Local 1 said Friday evening.

The strike could include upwards of 6,000 workers if employees at those hotels join. Their contract expired a week ago, and talks have stalled with the numerous hotel chains that are affected — although the hotels say they can weather the storm.

“We are disappointed to learn that Unite Here Local 1 has chosen to resort to a strike at this time,” read a statement from Marriott, whose workers are striking at six Chicago hotels.

“In the meantime, our hotels are open, and we stand ready to provide excellent service to our guests. While we respect out associates’ rights to participate in this work stoppage, we also will welcome any associate who chooses to continue to work.”

The strike follows a busy Labor Day travel weekend — and comes just weeks before the Chicago Marathon.

The main sticking point in negotiations is the year-round health coverage for employees, who can be classified as full-time but lose benefits if they’re laid off during the slow winter months.

“For the past 5 years I lost my health care 3 months out of the year — every year,” housekeeper Jessica Ramos said outside the Hyatt Regency Friday.

House attendant Q. Rivers, who works at the Palmer House Hilton, said in a statement that even if hotels have less business in the colder months, workers need benefits.

“Hotels may slow down in the wintertime, but I still need my diabetes medication when I’m laid off,” Rivers said. “They work us like dogs when it’s busy and then kick us to the curb in the winter.”

In addition to to health care, key points in collective bargaining talks include wage increases, job security, pensions, sick days and overwork.

“Striking hotel workers deserve sick days to see a doctor, workloads that keep them healthy and wages that keep up with the cost of raising a family,” the union said in a statement.

Union members voted on Aug. 15 to authorize a strike. A total of 3,218 members, or 97 percent of those who voted, gave the union negotiating committee the power to call for a citywide strike if necessary. The union represents more than 15,000 workers across the Chicago area.

Hilton joined Marriott in claiming the strike “will have minimal impact on our operations.

“We continue to provide the service and amenities we are proud to offer our guests and clients every day,” according to a Hilton statement. “We are negotiating with the union in good faith and are confident that we will reach an agreement that is fair to our valued Team Members and to our hotels.”

Negotiations were scheduled to continue throughout September, according to a statement from Hyatt’s Vice President of Labor Relations, Michael D’Angelo.

“We just completed our second negotiation meeting with Local 1 last week, where the union provided multiple proposals for the first time and indicated more will be forthcoming,” D’Angelo said. “Colleague benefits and wages remain unchanged as we negotiate a new agreement.”

Here’s where hotel workers are striking, according to the union:

Ambassador Chicago

Crowne Plaza Hotel Chicago-Metro

Doubletree Chicago Magnificent Mile

Drake Hotel

Hampton Inn / Homewood Suites Magnificent Mile

Hilton Chicago

Holiday Inn Mart Plaza

Hotel Blake

Hyatt Regency Chicago

Hyatt Regency McCormick Place

Inn of Chicago

JW Marriott

Kimpton Hotel Allegro

Kimpton Hotel Palomar

Kinzie Hotel

Millennium Knickerbocker

Palmer House

Ritz-Carlton Chicago

Sheraton Grand Chicago

W Chicago City Center

W Chicago Lakeshore

Warwick Allerton

Westin Michigan Ave

Westin River North

Wyndham Grand

The union also said that strikes are possible at the following hotels:

Cambria Magnificent Mile

Fairmont Chicago

Hotel Raffaello

Park Hyatt Chicago

Tremont Chicago Hotel at Magnificent Mile

Disclosure notice: Some labor organizations have ownership stakes in Sun-Times Media, including the Chicago Federation of Labor, which is affiliated with Unite Here Local 1.