Manny Pacquiao has been installed as an odds-on favorite for his WBO welterweight title defence against Shane Mosley but the Filipino has taken great pains not to underestimate his American challenger.

While Pacquiao is already acknowledged as one of the best offensive fighters of all time, he said on Wednesday he had not prepared for a fight in such intense fashion since he took on 10-times world champion Oscar De La Hoya three years ago.

"I have trained hard for this fight," Pacquiao, who has a career record of 52-3-2 with 38 knockouts, told a packed news conference at the MGM Grand's Hollywood Theater. "I am in 100 per cent condition. You know why?”

"Because I never underestimate Mosley. Mosley is a good fighter. Do you think he's old? He's not old. He moves like a 32-year-old, a 31-year-old. His hand speed and foot speed is still strong."

Mosley, a four-times world champion in three weight divisions, is a boxing veteran at 39 and many critics believe he is a shadow of the man who twice beat De La Hoya.

Yet it has often been said that styles make fights and Pacquiao knows full well that his American opponent, an agile and highly intelligent boxer, loves to attack.

"Mosley is not that easy (an) opponent," the 32-year-old Filipino, who was smartly dressed in a black suit and white dress shirt, said of their showdown on Saturday.

"He is a good fighter. He is strong, he throws a lot of punches and he moves fast. He is the kind of fighter you can't under-estimate."

Asked by reporters when he had last felt a similar level of concern preparing for a bout, Pacquiao replied: "The De La Hoya fight. De La Hoya throws a lot of punches, moves fast and is bigger and taller."

Pacquiao, moving up two weight classes for his first fight at welterweight, stunned De La Hoya with an eighth-round TKO in their non-title fight in Las Vegas in December 2008.

That victory confirmed the Filipino's pedigree and he has since won a further four fights, most recently an eighth world title in an unprecedented eighth weight class against Mexican Antonio Margarito in November.

Last week, Pacquiao's trainer Freddie Roach said his fighter had never prepared better for a bout, and he emphasized the point during Wednesday's news conference.

"We know we're in a tough fight," the bespectacled Roach said. "We respect Shane and his camp. They have a great team.

"But we are 100 percent ready. Everybody has worked really hard at this training camp. I think it's the best training camp we've ever had and Manny is in the best shape ever.

"We need to peak for this fight because Shane's one of the most crafty guys out there. He's intelligent and experienced and you can't replace experience, that's for sure."

Mosley, who has not competed in the ring since his draw with Sergio Mora in September, predicted an all-action contest at the MGM Grand Garden Arena on Saturday.

"This is going to be a terrific fight, a great fight," said the American, who is 46-6-1 with 39 KOs. "We're both warriors, we both love to fight and we're both winners.

"And when you get two winners in there, you know it's going to be a heck of a fight. So I'm excited. I'm ready. It's going to be a block-buster ... and I'm happy to be a part of this."

Pacquiao, like Mosley, is no lover of the trash talking that so often dominates the buildup to professional fights and he had a special message for those attending Wednesday's news conference.

"All of my life, I have had to fight," said the Filipino, who rose from poverty in his homeland to become a beloved sportsman and win a seat in his national congress. "As a child, I had to fight just to eat.

"The biggest fight of my life is not in boxing. No, the biggest fight in my life is how to end poverty in my country and this Saturday, I will wear yellow gloves (in the ring) as a symbol of unity and poverty."