Jennifer Lopez's beau Casper Smart is reportedly saving up for an engagement ring.

The 42-year-old superstar began dating 25-year-old back-up dancer Casper following the breakdown of her marriage to Marc Anthony last year. Casper is believed to be serious about Jennifer and is eager to propose. However, he is worried he won't be able to afford a band to match her expensive tastes.

"He's smitten, but said to pals recently, How am I going to find the money to buy Jen a good enough engagement ring?' Everyone was stunned because the relationship seems to be moving so fast, but his friends and family love Jen," said a source.

Wedding rumours circulated in December last year, when the couple were spotted browsing a jewellery store in Los Angeles.

Jennifer has appointed Casper "artistic director" of her upcoming tour, which will reportedly see him earn an impressive $40,000 a week. The star is also reportedly spending millions of dollars on her beau.

If Jennifer does tie the knot with Casper, it will be her fourth marriage following unions with Ojani Noa, Cris Judd and Marc.