Chinese solar companies expect the European Commission to announce within days a formal investigation into their alleged dumping of solar panels in Europe, which could result in heavy tariffs being imposed on them next year.

The expected move against the companies, whose share prices have tumbled and whose financial outlook is cloudy due to oversupply and falling solar-equipment prices, would come as they are already fighting clean-energy trade battles on several fronts.

Also, China and the European Union are at loggerheads over several other trade rows, including a European plan to punish airlines if they don't comply with an emissions-control program—issues that could have the potential to sour China's readiness to help in financially underpinning Europe's debt-laden economies.

European solar-panel makers filed a confidential complaint July 25 with the commission, the EU's executive arm, accusing Chinese solar-panel manufacturers of selling products at below-cost prices in Europe.