In a trading update, Pandora said it aims to generate around half of its revenue from rings, earrings and necklaces by 2022 and would increase its annual collections to 10 per year from seven.

The Danish firm also aims to increase the share of its owned stores in a bid to gain larger share of revenue and better be able to control its brand.

Pandora, which manufactures in Thailand, said higher production costs for more complicated jewellery and owning more stores would, however, put pressure on earnings. It forecast its 2018-2022 EBITDA margin at 35 percent, down from 39.1 percent in 2016.

It reported 2017 sales of 22.8 billion Danish crowns (2.71 billion pounds), up 15 percent in local currencies but below its own forecast of 23 billion to 24 billion.

Analysts had forecast sales of 22.9 billion crowns.

The biggest jewellery maker by volume said it expected its 2018-2022 sales to increase by 7-10 percent per year.

"The 2017 results are close to the targets we set ourselves at the beginning of the year, but we are of course disappointed to not fully reach the targets," Chief Executive Anders Colding Friis said, pointing to a difficult U.S. market and an 800 million crown foreign exchange loss on revenue.

Chief Financial Officer Peter Vekslund is stepping down and will be succeeded by board member Anders Boyer later this year, the company announced.

Pandora shares slumped on the news, trading down more than 14 percent at 569.4 crowns at 1036 GMT.

(Graphic for Pandora vs Denmark's benchmark index, click http://reut.rs/2CQj6kq)

Pandora shares rose by almost 20-fold in the four years to 2016, topping 1000 Danish crowns in May that year. They have since shed almost half their value hurt in part by a challenging U.S. market.

Recent volatility in the stock has in part been due to short bets by U.S. hedge funds.

(Reporting by Stine Jacobsen, additional reporting by Jacob Gronholt-Pedersen; editing by Susan Fenton and Jason Neely)

By Stine Jacobsen