Simon Cowell has stepped up his relationship with an American Idol make-up artist, whisking her away for a luxury vacation before his 50th birthday bash on Saturday.

The music mogul has previously dismissed reports he is dating 36-year-old Mezhgan Hussainy, insisting they are "just good friends". But he was more than happy to fly the beauty into Miami, Florida last week to join him for a private break, according to Britain's Daily Mirror.

The couple is said to have enjoyed five days basking in the sun and relaxing poolside at the Setai Hotel before jetting off to the U.K. for Cowell's lavish birthday celebration this weekend.

A source tells the publication, "Simon knew he wouldn't get too much time with Mezhgan at his big party so this was the perfect way for them to spend quality time together and give her his undivided attention."