June 2 - British online fashion firm ASOS posted a 41 percent rise in year profit, boosted by international expansion, and said it was on track to deliver on a plan for 1 billion pounds ($1.64 billion) of sales by 2015.

Asos UK website

ASOS, which targets internet-savvy 16 to 34-year-old women looking to emulate the designer looks of celebrities like Kate Moss, Sienna Miller and Alexa Chung, but at a fraction of the price, said on Thursday it made an underlying pretax profit of 28.6 million pounds in the year to March 31.

That compares with analysts' average forecast of 27.2 million pounds, according to Thomson Reuters I/B/E/S data, and 20.3 million pounds made in 2009/10.

Group revenue increased 52 percent to 339.7 million pounds, with UK retail sales up 25 percent and international sales up 142 percent, benefiting from the launch of United States, French and German websites.

While many UK retailers have struggled against tough macro headwinds, ASOS has prospered, benefiting from a young core customer base and the migration of spending from the high street to the Internet.

"We remain positive in our outlook for 2012 and are excited by the opportunities for both our UK and international businesses," said Chief Executive Nick Robertson.

Shares in ASOS have more than trebled over the last year, fuelled by buoyant trading and speculation the firm could attract a bid from companies as diverse as 20.3 percent Danish shareholder and supplier Bestseller, U.S. internet giant Amazon and British retailers Marks & Spencer and Tesco.

The stock closed at 2,367 pence on Wednesday, valuing the business at 1.78 billion pounds.

(Reporting by James Davey, editing by Rhys Jones)