Paul Smith says he has been given "an amazing shot" to prove himself against unbeaten super-middleweight champion Andre Ward.
Liverpool's Smith, 32, will fight Ward, 31, in a non-title catchweight bout in the American's home city of Oakland, California at 04:00 BST on Sunday.
It will be former Olympic champion Ward's first bout since November 2013.
"This is probably the only opportunity I will get to face such a great boxer," said British champion Smith.
"I would be a fool not to take it. It's an amazing shot and chance that I have been given.
"As always with me, you're going to get 100%. I'm going to give it every last thing I've got."
|Who is Andre Ward?|
|Born on 23 February 1984 in San Francisco, California, USA||Won Olympic gold at the 2004 Olympics in Athens|
|Signed a deal with boxing promoter Roc Nation owned by American rap artist Jay-Z||Was ranked world's second best fighter behind Floyd Mayweather by Ring Magazine|
|Stripped Carl Froch of his WBC super-middleweight title in 2011, winning on points||Has had a 19-month break from the ring after legal dispute with former promoter|
Ward has won all 27 of his professional fights, with 14 knockouts, and handed four-time world champion Carl Froch his second and only unavenged career loss in December 2011, at the Super Six tournament in Atlantic City.
Smith, meanwhile, has 35 wins and five defeats - his last loss coming against German Arthur Abraham in their WBO super-middleweight title rematch in February.
"Andre Ward is a quality fighter. He's a fighter that I have watched and admired for years," said Smith.
"It's hard not to be a fan of Andre Ward, but the plan is to show him what no one has ever done Saturday night and I'll be giving everything I can to do that."
Ward has not fought since beating Edwin Rodriguez in 2013, following a contractual dispute with former promoter Dan Goosen, who died in September 2014.
In January, Ward became the first high-profile fighter to sign with rapper Jay Z's Roc Nation Sports and is relishing being back in the ring.
|6ft 0in||Height||5ft 11in|
"Some people know what the absence was about. Some people don't know. I was tied up in litigation with my former promoter. It was a stance I had to take," he said.
"The fans were phenomenal. I would see them in the street and talk to them on social media and they kept saying, 'we want you back and we miss you.'
"That's why we brought this fight back to Oakland, as a thank you to the fans for your patience, diligence and for supporting me as long as they have.
"Smith's coming to win. I've prepared like I'm supposed to prepare. We want to put on a tremendous performance and let people know that Andre Ward is back and doing it in Oakland."
|What is catch-weight?|
|Boxers agree the weight themselves rather than fighting at a designated world-title weight.|
|Ward v Smith will be fought at 172lb rather than the super middleweight category of 160-168lb.|