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Beer aficionados are pouncing at the rare opportunity to buy one of the world's most elusive and revered beers for the first - and perhaps only - time in the United States.

It is called Westvleteren XII, and it is often hailed as the "world's best beer" by reviewers and fans.

Westvleteren XII is produced by Trappist monks in Belgium and sold at the abbey of Saint Sixtus in the Belgian countryside. The beer can usually only be purchased by reservation at the abbey - and reservations are extremely hard to come by.

But when the abbey found itself hurting for money for an expensive renovation, the monks reluctantly made the decision to sell the beer outside of the walls of the monastery on a one-time-only basis.

"I think it will be the last [time]," Westvleteren Brewery spokesman Mark Bode told NPR. "They say, 'We are monks, we don't want to be too commercial. We needed some money to help us buy the new abbey and that's it,' Back to normal again."

Beginning today, limited quantities of the beer are being sold in the U.S. and abroad. A number of stores have been sent "bricks" of the beer, which include six bottles and two glasses from the monastery. The gift box retails for $84.99.

"The phone has been ringing off the hook," Megan McBrayer, manager at New York City's Beer Table Pantry, told ABCNews.com. She said the store received 24 cases of the beer and has already sold many of them.

McBrayer said beer lovers are taken with "the whole mystique about it and the rarity of it."

"It consistently rates as one of the best beers in the world," she said. "It's been something that [beer lovers] have wanted for a long time, but it's been completely unattainable."