Ana Ivanovic, who begins her defence of the French Open this weekend, has secured a personal endorsement deal with private aircraft firm NetJets.

The company, owned by US investor Warren Buffett, also sponsors men's world number two Roger Federer, and will back Ivanovic for the next year. Ivanovic, like Federer, is a former world number one.

"The deal was signed this week, and it's a one-year, rolling contract," said Gavin Versi, Ivanovic's press agent.

Ivanovic has earned nearly US$7 million on court, and has earned significant sums off court through deals with sponsors including Nike and Adidas.