Angelique Kerber turns on the style to overwhelm Simona Halep at WTA Finals

Victory means the world number one has virtually booked a spot in the semi-finals of the elite eight-woman event.

Kerber, who beat Slovak Dominika Cibulkova in her first match on Sunday, was at her resilient best against Halep, putting her foot on the accelerator when she sniffed an opportunity to pull away.

The German entered the match trailing Halep, who beat Madison Keys in her Red Group opener, 4-3 in their head-to-head meetings but the 28-year-old showed flashes of the form that brought her two grand slam titles in 2016 to win in 82 minutes.

"I'm feeling very, very good here and it's just great to win my second match here playing my best tennis," Kerber said. "I'm trying to enjoy all my matches here and I hope the spectators can enjoy it as well."

Kerber came out flying, pushing Halep all around the court with her pinpoint groundstrokes to manufacture an immediate break, which the German consolidated with a gutsy hold after the Romanian set about attacking her opponent's second serve.

Halep was struggling to contain Kerber's main weapon, her whipped forehand, and while the world number four's athleticism and speed around the court kept her in the rallies, the German left-hander continued to dictate the early exchanges.

The Romanian, however, was showing more patience and opted to keep Kerber pinned on the baseline rather than going for winners, the strategy paying off as she worked her angles beautifully to break back then hold to love for a 4-3 lead.

Kerber was feeling the pressure but maintained her composure and consistency to first stave off her rampant opponent in the eighth game and then pressure Halep into a string of errors to cough up a decisive break of serve in the next.

The German held comfortably to seal a high quality opening set in 43 minutes and carried the momentum into the second when she reeled off her fifth game in a row to open a 2-0 lead before Halep finally stopped the rot by holding.

The Romanian threw everything she had at Kerber in the next game in an attempt to get the set back on serve but the top seed's remarkable retrieving skills and ability to hit winners while stretched out wide neutralised the threat.

Exerting all that effort for no reward seemed to knock the stuffing out of Halep and Kerber pounced again to seize another break against a demoralised opponent to give her the breathing room she needed to seal an ultimately comfortable victory.

Cibulkova takes on American Keys in the second Red Group encounter in a battle between debutants searching for their first victory of the tournament.