LAS VEGAS >> A group hoping to start running an adults-only "party train" between Southern California and the Las Vegas area said the deal has gone off the tracks.

Las Vegas Railway Express had planned to shuttle partiers from an Amtrak station in Fullerton, Calif., to the heart of Sin City in a club on wheels called the X Train.

A year-old agreement with Union Pacific allowed the company to use a rail line that’s currently limited to freight trains and hasn’t served a passenger line since Amtrak discontinued its Desert Wind service in 1997 due to low ridership.

In a Securities and Exchange Commission filing on Tuesday, Railway Express officials disclosed that the Union Pacific deal had fallen apart, and Union Pacific would be keeping the company’s $600,000 deposit.

The company painted a grim picture in its filing, though it insisted the project remains viable.

Railway Express said it still needs to raise $1 million for the California-Vegas route and added, "there is no assurance such funding will be available on terms acceptable to the company, or at all."

Railway Express CEO Michael Barron declined comment through a spokeswoman.

As recently as June, X Train backers had said they planned to start service on New Year’s Eve.

The train was supposed to offer cocktails, big TVs, recliners and two lounges for the five-hour trip. Tickets were going to cost $99 each way and include a meal and beverage, with plenty more alcohol available for purchase.

Tourists currently can’t get from Southern California to Las Vegas by rail alone.

Barron’s company wasn’t the first to try and fix that. A separate, much-talked-about XpressWest project proposes a high-speed train connecting Sin City to the region from which it draws 25 percent of its visitors.

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

In July, U.S. Department of Transportation suspended its review of a $5.5 billion loan request that would be critical for building the private bullet train, leaving the future of the project in jeopardy.