Paris Hilton has congratulated her sister on her engagement.

The 33-year-old heiress is delighted her younger sibling Nicky, 30, is to tie the knot with banker James Rothschild and can't wait to see her walk down the aisle as a ''beautiful bride''.

She wrote on Instagram: ''Congratulations @NickyHilton on your engagement!.

''I'm so happy for you! You will be the most beautiful bride! Such a lovely couple! Love you both so much!''

James - who has been dating the fashion designer for three years - proposed to Nicky while on holiday in Italy.

A source recently revealed: ''They went on a romantic anniversary trip over the weekend. He took her out on a boat into the middle of Lake Como and he proposed, got down on one knee and everything. It was incredibly romantic and beautiful.

''They are both really excited and incredibly happy.

''They are going on a road trip now throughout Europe and celebrating,''

James, who is based in the UK, started planning the special moment earlier this summer.

The source explained: ''Last month, he actually flew from England to the States to ask her parents for her hand in marriage!''

Nicky previously married her childhood friend and businessman Todd Andrew Meister at the Las Vegas Wedding Chapel in Las Vegas in 2004, but they were granted an annulment three months later and she admitted they had tied the knot ''on a whim.''