Katy Perry and John Mayer have once again said goodbye -- for now. The pop songstress, 28, and singer-songwriter, 35, have split for the second time, multiple sources confirm to Us Weekly. The high-profile pair began casually dating during summer 2012, and briefly called it quits back in August before reconciling the next month.
"It's sad," one pal tells Us, but cautions that it might not be a permanent break. "It's not over until it's over. You have to see how things play out." Adds another source, "She's leaving the window open. They have both been so focused on work."
Indeed, Perry has been busy recording her third studio album in Los Angeles, while Mayer -- on the mend following serious vocal problems and throat surgery last year -- is prepping for upcoming tour dates and a live Google Hangout chat this Thursday.
Following their September 2012 reconciliation, the twosome seemed to ramp up their relationship: The "Waiting on the World to Change" troubadour visited Perry's Santa Barbara, Calif., hometown in November, they attended high-profile events together as a couple, and Mayer, famous for his string of A-list exes, gushed about Perry in a January "60 Minutes" interview. "I'm very happy in all aspects of my life," said Mayer, who had messy splits with the likes of Jennifer Aniston, Jessica Simpson and Jennifer Love Hewitt, to name a few.
Perry, who finalized her divorce from Russell Brand in February 2012, was tweeting happily about her man as recently as March 2. "My boyfriend is taking me to a kitten shelter in his truck," she wrote to her nearly 34 million followers. "I can't think of a more perfect Saturday." But on March 18, she suggested she's been dealing with turmoil. "ATTENTION: Mercury is OUT of retrograde today. Thank GOD," Perry wrote.
Keep clicking to see more photos of the couple during happier times ...