Former world No.1 Venus Williams, resplendent in a floral dress and pink dreadlocks, showed glimpses of her old power by blasting past German Mona Barthel 6-3 6-1 to reach the second round of the Pan Pacific Open in Tokyo on Sunday.

No longer the force of old and currently only 62nd in the world, the 33-year-old American still had too much firepower for Barthel, taking just 63 minutes to sweep past her 34th-ranked opponent.

The seven-time grand slam singles winner, whose career has been blighted since being diagnosed with the autoimmune disorder Sjogren’s Syndrome in 2011, faces an uphill task to extend her stay, however, with top seed Victoria Azarenka – runner-up to Serena Williams at the US Open earlier this month – her next opponent.

Carefully coiffed braids poking through the top of her sun visor, Williams took the first set with a fierce forehand which caught the back of the baseline and wrapped up proceedings by bludgeoning a backhand past Barthel.

Williams celebrated with a polite curtsy to an appreciative crowd at the venue for the 2020 Olympic tennis.

Ninth seed Sloane Stephens, one of the new generation of American players, who once claimed the Williams sisters refused to sign an autograph for her at a tournament in Florida when she was 12, thrashed Switzerland’s Stefanie Voegele 6-3 6-2 to advance to the second round.

In other matches, twice major winner Svetlana Kuznetsova of Russia flattened Argentine qualifier Paula Ormaechea 6-1, 6-2 while 14th-seeded Belgian Kirsten Flipkens was tested in a 7-6 (7-4) 7-5 win over Czech Barbora Zahlavova Strycova, who also came through the qualifying draw of the 30th edition of the tournament.

Fifteenth seed Sorana Cirstea kicked off the $US2.3 million ($A2.45 million) event with a routine 6-4 6-4 victory over Julia Goerges.

World No.1 Serena Williams, who won her 17th grand slam singles title at the US Open, pulled out at the last minute due to fatigue while twice Pan Pacific champion Maria Sharapova withdrew with shoulder pain.