"It's been kind of on its way out in the last couple of months," the singer told the publication of his relationship with Koskinen, a Finnish entertainer and the 2007 winner of Finland's Big Brother.
"Sauli and I remain really good friends, and I know it's a cliché thing to say," he continued. "But it's totally true. I just gave him a coffee and bagel earlier today. He's a great person and we've had an amazing couple of years together. Things have just run their course."
Lambert added that both he and Koskinen have been increasingly focused on their own individual careers in recent months, which likely contributed to their breakup. "I've been getting really busy and traveling a lot and and he’s been getting really busy because he has a show he’s filming for Finnish television," he said. "So we just decided to part ways."