The marriage of pop singer Pink and her husband of two years, motocross racer and former The Surreal Life star Carey Hart, has ended, the singer's publicist, Michele Schweitzer, tells PEOPLE.

"Pink and Carey Hart have separated. This decision was made by best friends with a huge amount of love and respect for one another," says Schweitzer, adding, "While the marriage is over, their friendship has never been stronger."

Pink, 28, and Hart, 32, met at the 2001 X Games and broke up for a time in 2003, but the split was well behind them last June, when the singer defied convention and popped the question to her beau as he sped around the track during a competition in Mammoth Lakes, Calif.