* Governments in Asia threaten response to U.S. protectionism
* Some say U.S. solar investment and jobs may suffer
* Concens for wider global trade environment
* SMA Solar shares hit 4-week low (Adds more comment, share reaction in Europe; impact on US jobs)
By Henning Gloystein and Christoph Steitz
SINGAPORE/BERLIN, Jan 23 (Reuters) - U.S. President Donald Trump's decision to slap tariffs on solar panel imports is a blow to a booming global industry, and hit stocks in European and Asian solar groups on fears their business might suffer.
Although the move was intended to help American manufacturers, some in the sector said it would slow U.S. investment in solar power and cost thousands of U.S. jobs.
Trump on Monday approved a 30 percent tariff on solar cell and module imports, dropping to 15 percent within four years. Up to 2.5 gigawatts (GW) of unassembled solar cells can be imported tariff-free in each year.
The news sent SMA Solar, Germany's largest solar group, which makes 46 percent of its sales in the Americas, down 4.6 percent to a four-week low, while Norway's REC Silicon shed 1.2 percent.
German Finance Minister Peter Altmaier said the cost of solar products in the U.S. was likely to increase, and that Berlin would discuss the matter with Washington.
The U.S. has the world's fourth-largest solar capacity after China, Japan and Germany. Globally, solar capacity soared to almost 400 GW last year from under 10 GW in 2007, according to the International Renewable Energy Administration.
The U.S.-based Solar Energy Industries Association said the decision could cause the loss of around 23,000 U.S. jobs this year, and result in the delay or cancellation of billions of dollars in solar investments.
The U.S. government argued that its domestic manufacturers could not compete with what it said were artificially lower-priced Asian panels.
The Chinese firms that are the world's biggest makers of solar photo-voltaic cells will be hit by the tariffs at their production sites across Asia.
Jack Feng, vice president at Trina Solar, one of China's top panel makers alongside Jinko Solar, said his firm would "expand their territory to a broader range in the globe", including Europe, China, Indonesia and India.
China's Ministry of Commerce on Tuesday said the decision damaged the global trade environment, and the Ministry of Industry and Information Technology said Chinese solar companies were likely to curb overseas expansion.
"China's solar industry has been growing at a fast pace in recent years, making itself a target of protectionism in some countries," it said.
South Korea said it would "actively respond to U.S. trade protectionism", including exercising its rights under the World Trade Organization.
Morgan Stanley warned of wider economic damage as the protectionist stance "could challenge investors' perception whether the U.S. will adhere to current free trade policies".
There is still uncertainty on when the tariffs will be imposed and how the tariff-free imports will be shared out.
SMA Solar said it could not yet make a full assessment but added: "We do not expect a major collapse of the U.S. market."
Shares in U.S. panel maker SunPower climbed 0.8 percent on Monday and electric car maker Tesla, which also produces solar panels, gained 1.5 percent.
Yet analysts said the benefits for U.S. firms were not clear-cut. "The overwhelming majority of the 260,000 solar jobs in the U.S. depend on the cheaper imported products," Height Securities said.
Goldman Sachs estimated that the tariffs implied "a 3-7 percent cost increase for utility-scale and residential solar costs, respectively".
However, there remains the possibility of some manufacturers winning exclusions.
"Two key exclusions with respect to technology and certain countries (Canada/Singapore, among others) were included as part of the (initial) recommendation," Goldman Sachs said.
Canadian Solar is one the world's biggest panel manufacturers. In Singapore, unlisted REC operates one of the city-state's biggest manufacturing sites.
Doran Hole, Chief Executive Officer for North America at U.S.-listed ReneSola, said there may still be ways to settle the trade dispute.
"There is quite a bit of discretion about ... negotiations for a settlement. Having a global settlement would certainly be useful to the industry as a whole."
Additional reporting by Jumin Park and Jane Chung in SEOUL; Muyu Xu and Josephine Mason in BEIJING; David Stanway in SHANGHAI; Christoph Steitz and Vera Eckert in BERLIN; Nina Chestney in LONDON; Peter Maushagen and Alissa de Carbonnel in BRUSSELS; Editing by Kevin Liffey