World number two Novak Djokovic, enjoying a 24-0 winning record this season, said on Monday he was confident he can pass the supreme claycourt test by beating Rafael Nadal on the Spaniard's favourite surface.
"Nadal is the best in the world, he is dominant on clay, but this year I am playing against him with much more self-confidence," said Djokovic where he is top seed at the Belgrade tournament this week.
Djokovic has beaten Nadal twice this year, on the hardcourts of Indian Wells and Miami, but is stepping onto clay for the first time this season in his hometown.
Nadal "does impossible things because he improves his performance on the clay every year, although many believe that is not possible," Djokovic said.
"By such approach he is forcing all other tennis players to improve. He motivates me, (Roger) Federer and all the others to be better," he added.
Djokovic, who earlier this month was forced to pull out of the Monte Carlo Masters blaming a knee injury, said he was not burdened by a record-start of the season.
However, the number two said he had an ambition to win at least one more Grand Slam this year and get himself involved in fight for the number one position.