REFILE-UPDATE1-German engineer behind Chevy Volt arrives at Opel

(Refiles to change word to "blog" from "block" in last paragraph)

* Weber to head up product planning at German carmaker

* Weber returns after starting at Opel in 1991

* Opel boss Reilly promises investments in new product

(Adds details, background)

FRANKFURT, Nov 27 (Reuters) - The German engineer behind the Chevrolet Volt electric car will head product planning at General Motors' [GM.UL] Opel unit, a high-profile appointment that underscores the importance of the European brand to GM.

Frank Weber, a native of Wiesbaden close to Opel's headquarters in Ruesselsheim, returns to the German carmaker where he began his career after studying at the University of Darmstadt.

He follows retiring GM Europe Vice President Jamal El-Hout.

"The appointment of Weber is an acknowledgement of our commitment to develop environmentally friendly technologies for the future and the clear goal of launching the Opel Ampera electric car in 2011," Opel interim chief Nick Reilly said in a statement.

Earlier Reilly attempted to dispel union scepticism that the company wanted to return Opel to profitability on the cheap, skimping on investments in product and technologies.

"We have developed a sustainable plan for the future, including a breakeven target, which we expect to unveil in the middle of December," he wrote in a blog posting on a GM website.

"That plan will involve structural costs reductions. But importantly it will also include new product commitments, continued investment in research and development and an aggressive schedule for new model launches."

As product chief, Weber will be in charge of delivering on that pledge, and if successful could go a long way to improving relations with organised labour in Germany.