COPENHAGEN (Reuters) -Shares in Danish jewellery maker Pandora plummeted on Friday after the company flagged weakening sales in its key European markets, only partially offset by robust sales in the United States.

Its shares were down 12.6% at 0738 GMT and have lost 36% since a record high in January.

Pandora's sales totalled 7.08 billion Danish crowns ($1.11 billion) in the second quarter, slightly below the 7.17 billion forecast by analysts, with comparable sales growth slowing to 3% from 6% in the previous quarter, below the 4% growth expected by analysts.

In July, comparable sales grew 2%, it said.

Analysts at J.P. Morgan said in a note that they expected weak comparable sales in the second quarter and in July "to further add question marks regarding the sustainability of Pandora's growth in the short term, and to weigh on the stock."

The charm bracelet maker, however, kept its full-year guidance of 7-8% organic sales growth, with an operating profit margin of around 24%.

Comparable sales fell 9% in the UK, 7% in France and Italy, and 6% in Germany. 

Pandora said price rises and cost cuts would help it offset rising raw material expenses and the impact of tariffs on imports to its largest U.S. market.

Pandora, which makes all its jewellery at two factories in Thailand, is among the European companies most exposed to tariffs. 

The U.S. tariff rate for goods from Thailand was reduced to 19% from 36% announced in April after both countries struck a deal this month during President Donald Trump's broader overhaul of U.S. trade relations.

Pandora said the current level of tariffs would cost the company 200 million Danish crowns ($31.3 million) this year and 450 million next year.

It said it expected to be able to offset "a material part" of the effect of higher commodity prices, tariffs and foreign exchange rates "through a combination of pricing, cost efficiencies, and operating leverage".

Pandora would consider further price increases and new cost-cutting measures to cover the impact of tariffs, it said. The company raised prices by 4% in April and by a "low-single-digit" rate in August in response to higher commodity prices.

Silver, a key material for its jewellery, is trading near its highest level in 15 years.

Operating profit for the second quarter was 1.29 billion crowns, matching a forecast by analysts in a company-compiled poll. Organic revenue grew 8%, also in line with analysts' expectations.

($1 = 6.3907 Danish crowns)