The union represents nearly all nongaming workers at hotels and casinos, including housekeepers, waitstaff and kitchen staff. The union did not set a deadline for a walkout, but a full strike would effectively freeze all activity on the Las Vegas Strip, key to the city’s economy. More than 40,000 members are working without a contract as the union seeks better pay, benefits and working conditions in negotiations with top casino companies including, MGM International, Wynn and Caesars Entertainment.