"Based on its preliminary assessment, the European Commission, in order to clear the transaction, would currently ask for further remedies that Wieland is not obliged to offer under the agreed Sale and Purchase Agreement," Aurubis said.

Aurubis' shares fell more than 3 percent, underperforming the German mid-cap index.

The Commission said in August the sale might hurt competition and set a deadline of Jan. 17 to conclude a review.

Aurubis wants to sell the business as part of its strategy to expand into other metals besides copper. The division had turnover of around 1.3 billion euros ($1.5 billion) and output of about 230,000 tonnes of copper and alloyed products in its last business year.

"We will try to use the time until Jan. 17 to evaluate different options to make the process still happen," an Aurubis spokesman said.

"At the moment it is more unlikely than likely that the deal will happen."

The company said its executive board had identified strategic alternatives to the deal with Wieland in case the transaction ended up falling through.

Aurubis had said it was confident the deal would be approved.

(Reporting by Maria Sheahan in BERLIN and Peter Hobson in LONDON, editing by Riham Alkousaa and Jane Merriman)