Federer's serve was particularly effective against Nadal

The world number one made the vital break of serve in the ninth game of the first set before producing a string of incredible tennis to clinch the second.

Federer will now play David Ferrer, who continued his brilliant run of form with a 6-1 6-3 win over Andy Roddick.

The Spaniard is the only unbeaten player in the tournament.

The victory was Federer's most emphatic of his 14 encounters against Nadal.

606: DEBATE Outstanding match from Federer - his serving was just incredible merryTennis1

The pair had met in last year's Masters Cup semi-final and once again the result went in favour of the Swiss world number one.

The match began evenly as both players reached a 4-4 detente, but Federer began to impose his authority when he broke Nadal's serve at 5-4 to claim the first set.

And he unleashed an array of dazzling strokeplay to race to a 5-0 lead in the second as Nadal's resistance crumbled.

Although he managed to claw a game back, Nadal's misery finally ended when he returned a limp backhand into the net.

"Once I get on a roll it's hard to stop me," said Federer. "I'm exactly where I wanted to be and I've got a shot at winning the title, so it's a great feeling."

Federer has never lost to Ferrer in their previous seven encounters, but the Spanish number two is currently in the form of his life.

Ferrer rarely looked troubled against his American opponent

It took Ferrer just 28 minutes to win the first set against Roddick, breaking the American's serve three times in the process.

Roddick had called for the trainer in the first set after appearing to strain his back reaching for a high volley in the fifth game.

The treatment made little difference as Ferrer sent his legion of trumpet-playing fans into raptures when he wrapped up the first set with minimal fuss.

Roddick made a better start in the second set, but the turning point came in the fifth game when Ferrer returned a brilliant running cross-court backhand winner to go 4-2 up.

Ferrer had to fight back from three break points serving for the match at 5-3, but clinched his spot in the final when Roddick fired his return into the net.

The 25-year-old from Valencia has been in sensational form in Shanghai, but he believes he will be the underdog when he meets Federer on Sunday evening.

"I am not on the same level as Federer or Rafa," said Ferrer. "I am not the favourite for the final. I want to enjoy this moment."