The Calzaghe family are in Las Vegas on business. Expect trouble. And expect more hits than the final scenes of The Godfather. Enzo Calzaghe is a trainer with a machine-gun mouth. Joe Calzaghe, his son, is the world champion who has put away challengers for almost 12 years.

Calzaghe Jr has travelled to the USA for a fight for the first time. Bernard Hopkins is in his sights. The two boxing legends will meet at the 18,000-seater Thomas and Mack Centre for the light-heavyweight championship of the world.

Hopkins, at 43, has made his bones in the USA. Calzaghe has still to make the full force of his impact as a boxer known to the American continent. It is what drives him at 36. He has beaten all-comers at super-middleweight. Hopkins and destiny await at the 12st 7lb limit.

Calzaghe is the greatest British boxer of his generation. Behind Floyd Mayweather, he is the best pound-for-pound fighter in the world. Yet he is unknown to the great American public. A conversation with the boxer as he prepared to fly to Las Vegas was almost drowned out by USA reporters chipping in about the Welsh boxer's "tilt at greatness" next weekend.

Quietly spoken but strongly confident, Calzaghe makes more than polite noises in return. This is a boxer who has made 21 successful defences of his world title since he defeated Chris Eubank in 1997. He knows his worth. He is determined to prove it to Hopkins, the USA press and the world.

Enzo, 59, father and trainer, needs no further evidence of his son's greatness. This is a journey they have made together.

"If it wasn't for my dad I would not be where I am today," Calzaghe says softly. "I started boxing at nine. He took me to the gym, taught me the basics. When I wanted to knock it on the head and go out with my mates, he kicked me up the arse and kept me going on the straight and narrow."

The relationship survived a difficult spell. "There was time as a pro when I had some bad fights and people from the outside, even myself, thought about getting another trainer in. But after a few months I knew I could never do that because whatever happened in my career was down to him. So I stayed with my dad and he has proved with me, and the other boys he has made world champions, that he is a fantastic trainer. I would not change him."

Enzo had no fighting experience before taking Joe, cruiserweight Enzo Maccarinelli and light welterweight Gavin Rees to world titles. "For so long he did not get the recognition because he did not have boxing experience," says Calzaghe of his father. "But you can have great fighters who do not make good trainers. He is a tremendous motivator, he has tremendous knowledge of boxing. He always knows how to get the best out of fighters. He is devoted to the sport."

Rees and Maccarinelli both lost their titles last month. Many Americans believe Calzaghe will similarly come up short against Hopkins, a boxer who has captivated the world with a mixture of his criminal background and his ruthlessness in the ring.

Calzaghe, though, is a secret ready to be exposed in dramatic fashion. His defeat of Jeff Lacy, a fighter lionised by the American press, was so complete that Calzaghe, rightly, refers to it as a "humiliation" rather than a mere victory.

Hopkins, he believes, will be routinely beaten. This seemingly-outlandish statement is delivered without bravado. That adds to its force.

"I am always confident, no matter who I am facing. I am a winner. A champion. Undefeated for 18 years, this year," he says. "I look at a guy who is 43 and who has lost four fights. I'll make sure this fight is his last fight."

He is revelling at not being forced to sweat down to the super-middle-weight limit. "I don't have to starve to make 12st," he replies in answer to how his training has differed for a light-heavyweight fight. "Twelve stone was always difficult for me. Getting down to the weight drained my punching power and I have always been a big puncher. My natural weight is 14st 4lb. I'll be better at light-heavyweight. The speed is the same, the speed is always there, but the power will be different."

The American reporters then feed him a series of questions that suggest, ever so politely, that Hopkins might be an opponent too far for Calzaghe. He rebuffs this firmly. "A lot of Americans do not realise what I can do,' he tells us.

"I can box and I can fight. I adapt to anything I need to do in a fight. Hopkins is very good at what he does. He can be a bit of a dirty fighter as well. He's very clever. Whatever he has got, I've got better."

He adds, as if emphasis was needed: "I have fought some dirty fighters. I have been boxing 26 years. He can't outbox me, he can't outfight me. I'll do what I do."

Calzaghe has little time for the Barnum and Bailey bunkum that surrounds Las Vegas promotions. He is normally respectful in his pre-fight comments. The Hopkins fight is an exception.

"I'll retire if I don't beat this old man," he says. "I'll never show my face in public again. I'll throw more punches, land more punches. He will feel the power. I am aiming to sit on my punches a bit more and hurt him with the added weight. I want to knock him out."

This rhetoric is standard slugger fare but Calzaghe is much more than that. He has achieved genuine greatness in the select field of the boxing aficionado. His mission now is to demonstrate that peerlessness to the rest of the world.

It is why he has chosen Hopkins to fight. "Opponents matter. It is difficult to motivate yourself for an opponent you are not worried about,' he says. "The bigger the challenge, the more I relish it. I need a challenge."

It is why, too, Calzaghe has flown to Las Vegas. "I am going outside my comfort zone. He is a Golden Boy fighter, part of the corporation that is promoting the fight, so I do not have to just win, I have to record a proper win. I have to go there and dominate and that is going to be hard to do."

Calzaghe is aware that time is drifting away for him as he seeks to convert the USA public from benign ignorance to true belief in him. He has watched Ricky Hatton, the Manchester welterweight, make an impression over the Atlantic with his style and with the size of his travelling support.

"I want to end my career with meaningful fights, meaningful for myself," he says. "Seeing the tremendous reception that Ricky got in America, it was incredible. I got a buzz off that and I wanted bit of it. I love pressure. I want to show the American fans I am an excellent fighter. I want to show I am the best fighter in the world."

This, more than money, more than baubles in the form of a title belt, is what is on the line in Las Vegas. "I am a true champion," Calzaghe says firmly. Hopkins will feel the force of this obsession. Calzaghe v Hopkins will be shown exclusively live on Setanta Sports on April 19.