Eastbourne: Adam Helfant will step down as executive chairman and president of the men`s Tour at the end of the year, the ATP said.
"I recently informed the ATP`s Board of Directors that I have respectfully declined their offer to continue on," Helfant, who joined the ATP in 2009, said in a statement.
"Since I joined the ATP I have felt an immense sense of responsibility to the sport, and the people who have devoted the better part of their lives to it, to leave things better than when I arrived."
Helfant took over from outgoing executive chairman Etienne de Villiers and has continued where his predecessor left off in increasing revenue through sponsorship despite the tough economic times.
The American has also overseen a shortening of the men`s calendar which will come into force in 2012 and is designed to avoid the top players burning out.
"I am proud of what we`ve accomplished," he said. "Yet, there comes a time when it makes sense to look to the future and consider other opportunities. For me, that time is now."
Former world number one and 16-times grand slam champion Roger Federer said Helfant had made an important contribution to the success of the men`s game which is enjoying a golden period with Rafa Nadal, Novak Djokovic, Andy Murray and Federer himself all vying for grand slam titles.
"On behalf of the player council and all the players, I would like to thank Adam for his excellent leadership and contributions during his time at the ATP," Federer said in a statement.
"We achieved a lot together and will be sorry to see him go at the end of the year."