BERLIN (Reuters) - Daimler aims to cut costs at its Mercedes-Benz Cars group by 10-15 percent in 2009, German weekly auto motor und sport reported, without naming sources.

In the sales division, costs were to be reduced by up to 30 percent, it said in an article to be published on Thursday.

Mercedes' head of sales and marketing, Klaus Maier, told the magazine that Daimler had started a cost-cutting programme in early December to achieve annual return on sales of 10 percent and sales growth of 5 percent.

"But these targets cannot be reached every year, rather just as an average over the cycle," Maier said.

Maier also said he expected 2008 unit sales to reach the year-earlier level at Mercedes-Benz. In the eleven months through November sales had fallen 1 percent year-on-year.

To tap into expected demand for eco-friendly and fuel efficient cars in the future, Daimler now plans to cooperate with Evonik to develop batteries for electric cars, people familiar with the matter told Reuters on Saturday.

The two companies would found a joint-venture in which Daimler would hold a 90 percent stake and Evonik the remaining 10 percent, the sources said. They would develop batteries based on Evonik's lithium-ion technology.

In addition, Daimler planned to buy half of Evonik's battery unit Li-Tec, sources said.