LAS VEGAS — As if a weekend in Las Vegas isn’t wild enough for Southern Californians, a Nevada entrepreneur is about to add five more hours of party to either end.

After striking an agreement with Union Pacific Railroad last week, the Las Vegas Railway Express is one step closer to bringing to life the X Train, a luxurious “party train” complete with big screen TVs, recliners and two ultra lounges.

“The whole idea is when you get on a train, you feel like you’re in Las Vegas,” said Michael Barron, president and CEO of the $100 million venture that hopes to launch its maiden voyage on New Year’s Eve 2013. “It’s essentially a nightclub on wheels.”

Tourists can’t get from Southern California to Las Vegas by rail alone, and Barron’s company isn’t the first to try and fix that. The much-talked-about XpressWest project proposes a high-speed train connecting Sin City to the region from which it draws 25 percent of its tourists.

But it’s a multi-billion-dollar proposal that would require setting new tracks, and it’s often panned as a “train to nowhere” because the first phase would start in relatively obscure Victorville, about 100 miles outside of Los Angeles.

The X Train proposal calls for an Amtrak crew aboard a 576-passenger train that runs at standard speeds on traditional tracks.

It would start in Fullerton, Calif. — already home to an Amtrak station and part of Southern California’s Metrolink commuter train network — and end in downtown Las Vegas.

A conditional agreement with Union Pacific, approved Nov. 16, will allow the company to use a rail line that’s currently limited to freight trains and hasn’t served passengers since Amtrak discontinued its Desert Wind service in 1997 due to low ridership.

Tickets for the adults-only train would cost $99 each way and include a meal and beverage, with plenty more alcohol available for purchase. To keep ticket prices low, the company would try to make money booking Las Vegas hotels and entertainment for passengers.

With initial plans for one trip a day on Thursday, Friday, Sunday, and Monday, Barron believes he can attract tourists weary of the weekend traffic gridlock and perhaps hung over from their weekend revelry.

“Sunday is horrific,” Barron said of the Interstate 15 corridor that links Las Vegas and its neighbor. “So now you’ve been up for 40 hours gambling and you have to drive for seven hours — that’s just horrible. But people do it in spite of that!”

Tom Skancke, a transportation consultant for the Las Vegas Convention and Visitors Authority, pointed to the proposed trains and other alternatives to personal cars as options that could entice a new generation of tourists. A new Greyhound Express nonstop bus route between L.A. and Las Vegas launched earlier this month.

“These modes of transportation do appeal to a younger, more eco-friendly traveler,” Skancke said. “This generation is more interested in passenger rail, transit and high-speed rail than previous generations.”

There’s still work to be done on the X Train to get it running by late 2013. The sixteen cars the company has purchased need to be renovated, and a station needs to be completed in downtown Vegas.

“We’re four years and $12 million into it. It’s a lot of infrastructure building,” Barron said. “This is a simple concept in discussion, but it’s complicated to do.”