The possibility of 50,000 Las Vegas casino workers going on strike drew closer Thursday, with their contracts expiring at midnight and the prospects of new ones still uncertain. The bartenders, housekeepers, bellmen and other unionized workers at 34 casino-hotels on the Strip and downtown Las Vegas have been negotiating new five-year contracts since February. But wages, workplace training and other issues have kept their union and employers from reaching agreements, pushing employees to authorize the first strike in more than 30 years at any time starting Friday. Here's a look at the negotiations and a possible strike: