By Stine Jacobsen

COPENHAGEN (Reuters) - European wind shares fell on Tuesday after U.S. President Donald Trump axed support for new offshore wind power on his first day in office, adding to pain in an industry that had turned to the United States to help revive its fortunes.

The biggest decliner, Denmark's Orsted, which plunged 17%, came under further strain from impairments on its U.S. ventures.

The global offshore wind industry, which initially boomed, has been struggling to deliver the carbon reductions pursued by many governments as escalating costs, supply chain issues and planning issues have slowed development.

U.S. prospects for wind had looked more favourable because of former president Joe Biden's green investment policy.

But Trump, long known to favour fossil fuels, on Monday suspended new federal offshore wind leasing pending an environmental and economic review, saying wind turbines are ugly, expensive and harm wildlife.

Orsted on Tuesday reported 12.1 billion Danish crowns ($1.69 billion) in impairment charges related to the U.S. offshore market, triggering a selloff that dragged its share price to some 84% below a peak in 2021.

A delay and higher costs for Orsted's Sunrise Wind project, which is expected to be the largest U.S. offshore wind farm once completed, were the main reason for the plunge, analysts said.

But the company also flagged impairments on seabed leases that could be directly linked to Trump, Sydbank analyst Jacob Pedersen told Reuters.

"Orsted now has some assets in the U.S. that are worthless. If there is nothing to be built because of Trump, Orsted can neither sell nor use the leases," he said.

Other companies, including wind development companies, fell by smaller percentages.

Portugal's EDP Renovaveis shares fell by around 1.6%, Germany's RWE shed around 0.5%, Norway's Equinor dropped by 2.2% and wind turbine manufacturer Vestas fell by nearly 3% in afternoon trade.

Italy's Prysmian, the world's biggest cable maker and a major player in offshore wind transmission, on Tuesday said it would abandon a plan to build a plant in the United States to make cables for offshore wind parks.

Its shares, which closed at a record high on Monday, lost around 1% on Tuesday.

RWE SAYS NO IMPAIRMENT

Germany's RWE, the world's second-largest offshore wind project developer after Orsted, said there was no need for impairments on a 2.8 gigawatt U.S. offshore wind project it is jointly developing with Britain's National Grid.

"The Executive memorandum on offshore wind did not come as a surprise," the company said. "We currently see no need for impairments as the seabed lease is valid for at least until the 2060s, so it's a long time to go to realise the project at a later stage."

EDPR and Vestas declined to comment.

Vestas secured an order from Equinor last year to power New York's Empire Wind 1 offshore wind project, while EDPR has a 50-50 offshore wind JV with Engie called Ocean Winds that is developing the Southcoast Wind project off the coast of Massachusetts, due to begin construction late this year.

Germany's vice chancellor Robert Habeck told a conference in Berlin that Europe needs to continue expanding low-carbon energy during the Trump presidency, regardless of policies and his planned withdrawal from the Paris climate agreement.

The American Clean Power Association (ACP), a U.S. clean energy industry group, said it strongly opposed Trump's executive order on wind leasing and permitting.

"States voting for President Trump are eight of the top 10 states in terms of reliance on wind power with many depending on wind for a significant share of their electricity use.  Restricting wind development in these regions is certain to increase consumer energy bills," it said.

Although opposing wind, Trump issued a flurry of orders intended to boost energy production from other sources, driving up shares of U.S. nuclear power companies.

($1 = 0.9614 euros)

(Reporting by Stine Jacobsen in Copenhagen, Amanda Cooper in London, Giulio Piovaccari in Milan and Alessandro Parodi in Gdansk; Vera Eckert in Berlin; Christoph Steitz in Frankfurt; writing by Nina Chestney; editing by Terje Solsvik, Louise Heavens and Barbara Lewis)