NEW YORK (Reuters) - Featherweight title holder Conor McGregor has promised the Irish will claim back New York when he fights Eddie Alvarez for the lightweight title at UFC 205 in an attempt to become the UFC's first two-weight champion.

Dressed in a sharp pin-striped blue suit, the brash 28-year-old predicted he would knock Alvarez out in the first round on Nov 12 to become the first UFC fighter to hold titles in two weight classes simultaneously.

"The Irish, we built this damn town. We built this city. Now we're back, we're coming to claim what's ours," he told a rowdy media conference at Madison Square Garden on Tuesday.

"I run New York, I run this whole ship and 'Mystic Mac' predicts I will knock you out in round one," he told Alvarez.

McGregor was crowned featherweight champion on Dec 12 last year when he scored a knock-out over Jose Aldo in just 13 seconds, while Alvarez claimed the lightweight belt with a first-round KO win over Rafael dos Anjos in July this year.

UFC 205 will be the first major mixed martial arts event in the state of New York since the ban on the sport, imposed in 1997 and which lasted for almost 20 years, was recently lifted.

With a strong card featuring three world titles fights the event is likely to sell out quickly. But McGregor, who claimed he is set to make US$40 million (S$54.44 million) this year, was in no hurry to reveal what he planned to do next if he does hold both belts.

"I'm going to wrap one on one one shoulder, another on the other shoulder, and they're going to need an army to get them off me," a grinning McGregor said.