Britney Spears celebrates sons' birthdays

Britney Spears has expressed her hopes to be the "best mommy" she can be as she celebrated her sons' birthdays.

The mum of two took to Instagram to write tributes to Sean Preston, whose 21st birthday is on Monday 14 September, and Jayden James, who turned 20 on Saturday 12 September.

In a post compiled for her younger son, she wrote, "Happy birthday to my handsome young boy, oh dear lord, we have this beautiful thing called life in front of us. It's such a beautiful delicate thing. I hope I can be the best mommy in the world every day of ur life!"

The Grammy winner included a photo of Jayden during a photoshoot and another of him as a child.

In a separate post, she shared a throwback photo of herself with Jayden and Preston as toddlers.

"Happy early B-day to u as well," Spears wrote in a tribute to Preston.

"Please stop working out so much because your muscles r starting to scare me... JK! I'm so proud of the young man you have become."

Additionally, Spears shared two separate photos of her sons with the same caption that read, "Happy b day baby!"

The Toxic singer shares Jayden and Preston with her ex-husband Kevin Federline, to whom she was married from 2004 to 2007.