Founder and managing director Mahesh Bhupathi said he had received reassurances from Federer's camp as the clock ticks down to the innovative tournament's debut season.
"We spoke to them. He's fine, he's playing Davis Cup this weekend," Bhupathi told AFP in Singapore, one of four venues for the IPTL which starts in Manila next week.
A possible withdrawal by Federer, who pulled out of Sunday's World Tour Finals decider but is playing the Davis Cup final against France this weekend, would be a major blow to the IPTL.
Bhupathi said he hoped the made-for-TV IPTL, which puts a limit on match-times and features a shot-clock, DJs and cheerleaders, would become a strong draw for players even at the end of a long season.
"We've created this exciting format and they'll hopefully schedule us along with the four Slams and they can work around it," he said at the launch of the Singapore Slammers team.
"People say that the season is long but we're creating something that is exciting enough for them to come so that they'll automatically schedule us."
Teams representing Manila, Singapore, New Delhi and Dubai will play each other in the four cities in a mini-league packed into a compact schedule of about three weeks.