AFP - The Spanish government warned on Friday that an Opel auto plant could be closed down if workers refused to ratify a deal between unions and Canadian auto parts maker Magna International.

"If the workers reject the proposal it would be a very bad option" as Magna "has not yet sealed the sale with General Motors and would probably choose to pull out of the plant," Industry Minister Miguel Sebastian told Spanish National Radio.

Magna and unions at the Opel factory in Figueruelas, northern Spain on Thursday reached a preliminary deal on its future.

The agreement envisages the loss of 900 of the more than 7,000 jobs at the factory, less than the 1,300 Magna had sought when the talks began last week and around half the number it had originally proposed.

Magna also undertook to maintain the bulk of the production at the plant of Opel's five-door Corsa, Merival and other models. Unions had feared some of the production would be moved to Germany.

Sebastian on Thursday hailed the deal, saying "the future of the factory is guaranteed for 10 years."

The workers are scheduled to vote on it on Monday, and until then unions said are they are maintaining plans to hold two 48-hour strikes for late October and early November.

Struggling US giant General Motors last month announced the sale of a majority stake in its loss-making European arm Opel to Magna and its partner, Russian state-owned lender Sberbank.

Magna is reportedly planning to cut 10,500 Opel jobs across Europe.

The deal was supposed to be finalised last week but was criticised by the European Commission owing to a clear preference by Berlin for Magna's bid over several alternatives.

The EU commission is now awaiting confirmation from GM that the sale was decided according to commercial and not political criteria.

Sebastian said "we must speak to the German government" over possible aid for Opel if the deal goes ahead.

Berlin, keen to protect as many of the 25,000 Opel jobs in Germany as possible, has offered up to 4.5 billion euros (6.7 billion dollars) in state aid.

But it wants other European countries where Opel has factories, including Britain, Spain, Poland and Belgium, to provide some of the promised aid.

These countries have however been reluctant to make firm commitments amid concerns that the money would effectively secure German jobs at the expense of their own workers, and they have pressed Brussels to examine the deal.