Katy Perry (R) and John Mayer [Photo/Agencies]

The 36-year-old 'Wildfire' hitmaker is expected to propose to 'Roar' singer, who split from British comedian Russell Brand in December 2011 after 14 months of marriage, in the near future.

A source told E! News: "It's inevitable."

The insider said that the couple are "very serious" and added: "Everyone wants them to get engaged. They are so perfect together."

Katy recently gushed about her feelings for the singer-songwriter, whom she first started dating in June 2012.

She said: "I actually am dating my crush. I had a crush on him for a long time."

She also insisted she loved being married even though she got a divorce.

She said: "Of course. I really loved it. It was a new, fun, exciting journey. But I like how I am now, and I think all things happen for a reason."

John, who previously dated Jessica Simpson and Jennifer Aniston, presented the 29-year-old star with a heart-shaped ruby ring for Valentine's Day in Santa Barbara, California, earlier this year but a source insisted at the time that they weren't ready to tie the knot.

The insider said: "It's a one-of-a-kind Daniel Gibbings ring featuring a 12 carat ruby high-dome cabochon heart shaped centre, accented by two teardrop faceted sapphires and rubies, set in 20-carat gold."