Clijsters triumphed at Flushing Meadows earlier this month after an 18-month break to have a baby while Henin announced her return on Tuesday after more than a year off.
"Justine worked very hard in the past to get magnificent results in her first career, Clijsters said on her website.
"For tennis it's fantastic to see her come back. It's very good for women's tennis and very good for Belgium."
Former world number one Henin, 27, announced she had rediscovered the desire to play after 16 months in self-imposed retirement.