Rafael Nadal complains that the 50 percent tax put on players' appearance fees, winnings and a proportion of their worldwide endorsement earnings in the United Kingdom is putting the year-end ATP World Tour Finals in London at risk.

"It is really tough what is happening today in the UK with the tax,” Nadal told reporters. "There are a lot of things that are really positive. This (tax) thing is probably really negative. What I believe in my heart is that London is a fantastic event. There's a full crowd at every match, a fantastic stadium. But London is not the only city in the world. The tax regime from UK is complicating a lot of things because to go and play at Queen's, the problem is not to win. The problem is I can lose money because I go there. I play for one week, and they take out money from my sponsors. That's a lot. I'm going play at Wimbledon. I'm going to play in the World Tour Finals. So that is a lot of weeks, a lot of tax. It is becoming more and more complicated to play in the UK at the moment. So (if there is a tax) change, the chances of keeping the World Tour Finals in London are going to be very, very high."

Nadal is estimated to earn around $21 million in endorsement income annually. He just announced that he would play the Wimbledon warm-up tournament in Halle, Germany next year rather than in Queen's Club, but denied that he made the change because of a reported $1.2 million dollar appearance fee.

London has a five-year contract for the ATP World Tour Finals that comes up for renewal in 2013.