Courteney Cox [Photo/Agencies]

The former 'Friends' actress, who started dating the Snow Patrol frontman in September, was spotted wearing a huge diamond ring on her engagement finger as she strolled through Los Angeles International Airport (LAX) with the rocker on Sunday.

A source told Us Weekly magazine that their wedding will be "sooner than later" and "they are talking about having a child together."

The 37-year-old Northern Irish singer's close friend Ed Sheeran recently predicted that the couple, who moved in together last month in LA, would tie the knot in the future.

He said: "I wouldn't be surprised, but it's still early days.

"They certainly enjoy each other's company and feel very comfortable with each other."

The 23-year-old British singer later said: "I'm not sure that it's public knowledge, so maybe I shouldn't have said anything - but, yes, they're already living together. Things are moving fast. He moved in and, judging by the last time I saw them, they couldn't be happier."

Courteney, 49, was previously married to David Arquette with whom she has a nine-year-old daughter, Coco, and her ex-husband has given her relationship with Johnny his seal of approval.

An insider said: "What has really impressed Courteney is how good Johnny is with Coco.

"She didn't let any other men near her daughter but he's always out in their grounds playing sport with Coco and bonding with her.

"Also, David approves of him - they've met a few times and are even planning a dinner with David and his partner Christina. They're all comfortable around each other. Johnny doesn't feel at all awkward about it."