FIRST OFF . . .

Striking Las Vegas musicians extended their picket lines Monday to the Las Vegas Hilton, a day before singer Engelbert Humperdinck was scheduled to open in the resort’s main showroom. The Hilton became the fifth major resort to be officially struck by the musicians, who decided to picket the hotel after walking out of talks last week with the resorts. A Hilton spokesman said he didn’t know if Humperdinck would perform as scheduled beginning tonight. Humperdinck was traveling from England to Las Vegas and was not available for comment. Several entertainers have canceled their performances at Caesars Palace, which is also being struck by the musicians, and Bally’s has closed its celebrity room indefinitely because of the strike. Musicians are also striking the Flamingo Hilton and the Tropicana over their decision to fire most of the musicians in their production shows in favor of taped music. The strike began June 1 at the Tropicana and spread to the other resorts in July.