Manny Pacquiao lands a punch before defeating Joshua Clottey at their WBO welterweight title fight in Dallas. AFP

Filipino boxing icon Manny Pacquiao was a master at work Saturday night (Sunday, Manila time), scoring a unanimous victory over Ghanian Joshua Clottey to retain his World Boxing Organisation Welterweight title before 51,000 fans at Cowboys Stadium in Arlington, Texas.

Pacquiao dominated the 12-round duel with an impressive display that underscored his status as the world's top fighter. With the win, Pacquiao extended his winning streak to 12.

"I controlled the fight after the first round," said Pacquiao, who has been named Fighter of the Decade.

But Pacquiao was frustrated by Clottey's defence and the challenger's decision to cover up and not throw more punches than he did.

"Clottey is not an easy opponent he is very strong," Pacquiao said. "He took a lot of punches and was never hurt."

In the fourth round, Pacquiao tried to get Clottey to come out of his defensive shell and at one point tapped both of Clottey's gloves in a failed attempt to get him to trade blows.

Pacquiao, 51-3 with two drawn and 38 knockouts, has looked unstoppable in his previous three fights against opponents who were willing to engage him in the middle of the ring.

Clottey, who fell to 35-4, lasted all 12 rounds with a game plan that included counter-punching and covering up. By the middle rounds it was apparent Pacquiao had a victory sewn up.

But Clottey said he didn’t feel Pacquiao's power but was bothered by the boxer's hand speed.

Pacquiao's punishing assault was reflected on all three judges scorecards as he won by scores of 120-108, 119-109 and 119-109.

"This fight is dedicated to all of you, especially to the people in the Philippines," Pacquiao told the crowd from the centre of the ring.

“Right now I am so happy because of the support I have from my fans. This is the first fight in my career where there is a lot people coming,” he said.

The fight, part of the first boxing card at the US$1.2 billion state-of-the-art home of American football's Dallas Cowboys, was watched by one of the largest crowds in US boxing history.

Pacquiao, who last lost to Erik Morales in March of 2005, defended his title on the same date he was to face unbeaten American Floyd Mayweather before negotiations broke off over a drug-testing dispute.

With Clottey out the way, Saturday's victory could set the stage to reopen talks between Pacquiao and Mayweather's camp.

“I want that fight because people want that fight,” said Pacquiao.

But first, Pacquiao plans to try his luck at politics and run for a congressional seat in the Philippine national election in May. He ran for Congress in 2007 but failed to get elected.