Six L.A. area hotels agreed to lock out 2,380 unionized workers after Unite HERE members walked off the job at the Hyatt West Hollywood, a member of a bargaining group with the other six hotels.

The Los Angeles Hotel Employer’s Council voted late Thursday in favor of the lockout after about 120 workers struck the Hyatt West Hollywood over health care reimbursements. The hotels said the lockout would not take effect until midnight Saturday, giving the union time to accept a “best and final” contract offer.

“This is what we call a defensive lockout it comes in response to a strike,” said Fred Muir, consultant to the hotel council.

Tensions have been high since a contract between Unite HERE Local 11 and nine large hotels expired in April 2004. (Two have since dropped out.) The union has been seeking to align contract expiration dates throughout the country in 2006. The hotels have offered substantial pay increases but they want a longer contract.

The health care payments arose from earlier negotiations. To put pressure on the union, the hotels began deducting $40 in monthly health care premiums last July, but then stopped making the deductions in January. Since then, the union has been seeking reimbursement for premiums the workers paid in the interim.

David Koff, research analyst for Unite HERE, said the local’s 2,500 workers were forced to pay more than $650,000 in health care premiums.

“This has been an issue that agitated the workers from the beginning,” said Koff. “We started at this hotel but it could expand.”

The union is looking for a two-year agreement that would be retroactive to April 15, 2004, when the previous contract expired. That would line Local 11’s agreement with those in several other cities, giving the union more bargaining power.