UPDATE 2-GM to present Opel restructuring plan in Dec

* Interim GM Europe head says to cut Opel capacity by 20 pct

* Says not sure yet about site closures

* Targets 900 job cuts in Spain, similar to Magna plan

* To ask Spain for state aid

* Says plan will not favour Germany

(Adds details on Spain job cuts, Germany, aid)

By Feliciano Tisera

ZARAGOZA, Nov 19 (Reuters) - U.S. carmaker General Motors GM.UL will present a new viability plan for Opel in mid-December as it aims to reduce capacity across Europe by about 20 percent, a top executive said on Thursday.

GM this month reversed a decision to sell a majority stake in Opel to a consortium led by Canadian car parts manufacturer Magna MGa.TO.

Magna was targeting about 900 job cuts in Zaragoza, and Opel's union representatives in Spain have told Reuters they would not accept any more cuts than those negotiated with Magna.

"Our plan is very similar to Magna's. I don't think it's worse," Nick Reilly, interim head of GM's European business, told reporters in northern Spain, where Opel's largest plant is located.

Reilly, a Briton who is in charge of restructuring Opel until ex-GM Europe boss Carl-Peter Forster is replaced, has said up to 10,000 jobs could go across Europe as part of GM's overhaul. [ID:nLH070856]

However, on Thursday he said it was too soon to say whether any production sites would be closed.

"We'll try not to do it, but we still don't know how we're going to carry out the production cuts," Reilly said.

NO SPECIAL TREATMENT FOR GERMANY

GM's new scheme will not transfer production from Zaragoza's Figueruelas plant, which has a reputation for being Opel's most profitable, to Eisenach in eastern Germany.

Magna's deal, backed by German Chancellor Angela Merkel, had met with criticism by Spain for plans to transfer a chunk of production to Germany.

"We'll base all of our decisions on economic and industrial criteria, not political," Reilly said, and added that Germany would not receive any special treatment.

GM is seeking European aid for its restructuring plan and will ask Spain to hand up cash when Reilly meets with the country's Industry Minister, Miguel Sebastian, on Friday.

GM is seeking $3.3 billion for its overhaul in Europe, compared with Magna's $4.5 billion plan.

"First we have to see GM's plan and then we can talk about the financial aspects and possible aid," an Industry Ministry spokesman said. (Reporting by Feliciano Tisera; Writing by Tracy Rucinski; Editing by Jon Loades-Carter)