* Q4 EBITDA at polysilicon unit down 53 pct
* Q1 to be diffcult - CFO
* Shares down 1.9 pct (Recasts with CFO comments, background, updates shares)
By Christoph Steitz and Jens Hack
FRANKFURT/MUNICH, Feb 7 (Reuters) - Wacker Chemie said rising demand in China and the United States had halted a slide in the price of polysilicon, potentially brining an end to years of margin declines for a key ingredient needed for making solar panels.
"It looks as if prices for polysilicon have reached a floor," Chief Financial Officer Joachim Rauhut said, adding the world's No.2 maker of polysilicon still had a tough first quarter ahead of it.
An oversupply of modules and a cut in government subsidies sent prices for polysilicon plunging by 47 percent in 2012, causing the group to report a 29 percent drop in core profit over the same year.
The crisis has forced polysilicon makers - including Wacker Chemie, sector leader Hemlock Semiconductor and Norway's Renewable Energy Corp - to review production plans, reduce working hours or cut jobs.
Western polysilicon makers have also come under pressure from a trade war in the solar industry, with China launching anti-dumping and anti-subsidy investigations into imported European Union solar-grade polysilicon.
"The pending punitive tariff decision from China's Ministry of Commerce ... could represent a further downside risk to earnings for international poly producers," HSBC analyst Christian Rath said.
Polysilicon is Wacker Chemie's cash cow unit, accounting for about a quarter of group sales and about 54 percent of earnings before interest, tax, depreciation and amortisation (EBITDA) in 2012.
In the fourth quarter, core profit at the unit more than halved to 78 million euros ($106 million).
Rival Hemlock Semiconductor is a joint venture between Dow Corning, Shin-Etsu Handotai and Mitsubishi Materials.
Other competitors include Korea's OCI Co Ltd and China's GCL-Poly Energy Holdings. ($1 = 0.7387 euros) (Editing by Jonathan Gould and David Cowell)