Tennis: Ace endorsement contract for Serena Williams

Serena Williams, 21, is close to signing an endorsement contract with Nike, a deal that could be the richest for a female athlete.

The multi-year agreement would include royalties and performance bonuses for winning Grand Slam tournaments or reaching No 1 in the rankings. Those clauses could make the contract worth more than the deal with Reebok that Williams' older sister, Venus, signed in December 2000 after winning Wimbledon and the US Open. That was worth up to US$40 million over five years.