When asked by E! News on Tuesday for the reason behind the break-up, Chmerkovskiy said it was a "little personal."
"It's a little rough right now," he told E! News outside West Hollywood's 3rd Street Dance Studio.
Smirnoff and Chmerkovskiy made their Broadway debut last month in Burn the Floor and are also scheduled to dance at the 61st Annual Primetime Emmy Awards on September 20, which E! News confirmed they intend to follow through with.
With both of those commitments on-top of training forDancing with the Stars' upcoming ninth season, the couple recently told E! News they had decided to delay their wedding until next summer.
"The only thing we've decided on is next year in June," Karina told E! News at the time. "We were supposed to pick the place, but we've never actually had the time to go further... As long as we're together, tying the knot is a plus. It's something extra."
Dancing with the Stars ninth season will premiere with a two-hour performance episode on Monday, September 21 at 8PM ET/PT. Chmerkovskiy is partnered with actress Debi Mazar, while Smirnoff will be competing with singer Aaron Carter.