VISTA, Calif. (AP) — The father of retired tennis star Mark Philippoussis pleaded not guilty Thursday to molesting two 9-year-old girls while he was a private tennis instructor in California.

Nikolaos Philippoussis, 68, entered pleas to 14 counts of committing lewd acts and sex acts with children. He could face life in prison if convicted.

Philippoussis is accused of molesting two of his tennis students for more than a year, beginning in June 2016.

Prosecutors say the encounters took place at his home, in his car and at a San Diego County country club.

Philippoussis was arrested Tuesday at his San Diego home. At the hearing Thursday, his bail was raised from $2.5 million to $9.2 million.

"It is quite a colossal amount," defense attorney Ryan Tegnelia said.

Philippoussis, an Australian citizen, was ordered to surrender his passport if he does make bail, but his attorney told the San Diego Union-Tribune (http://bit.ly/2eRKjft ) that was impossible.

Philippoussis's son Mark Philippoussis was in court for the hearing but declined to comment, the newspaper reported.

He is a two-time Grand Slam finalist who ranked as high as eighth in the world and helped Australia win the Davis Cup in 1999 and 2003.

Philippoussis was his son's coach for much of that career.

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This story has been updated to show Philippoussis entered the pleas Thursday, not Wednesday.