"I want all my fans to know that the WTA Tour is forcing me and several of the other top players to do a four-hour commercial shoot for WTA Tour marketing materials," Sharapova told her website.

"They want me to do this shoot on Sunday, Monday or Tuesday of the Rome tournament after flying 12 hours from LA.

"I have set my own personal rules when it comes to doing shoots and I never do shoots before tournaments because they are mentally draining and I want to just focus on my tennis.

"Now the WTA is telling me if I don't do this shoot they will fine me over US$300,000. As you can see the WTA Tour loves to fine players.

"To be honest, I would love to do this and help promote the tour as much as possible, but to force me to do this shoot the day before a Tier I tournament is just not right."

The WTA insisted players were aware of their obligations.

"Players have many obligations both on and off the court, and what is being asked of players in Rome is in the rules," a spokesman said.