Spanish unions have reached an initial agreement with Magna over its proposed takeover of automaker Opel, leading trade union groups said on Thursday, clearing one of the last obstacles in the way of a deal with parent GM.

Following a meeting between Magna, the UGT and CCOO unions and central and regional government representatives, the Canadian company has agreed to keep the plant in Figueruelas, in the northern region of Spain, which manufactures the Corsa model, intact until the summer of 2011.

We have reached agreement in principal over an industrial plan for the Figueruelas plant which guarantees production capacity and planned job cuts are less traumatic than initially announced, a spokesman for UGT said.

GM CEO Fritz Henderson told CNBC on Wednesday that the signing of the Opel deal -- which has been delayed by last minute negotiations over jobs and competition concerns voiced by European Union regulators -- could take place as soon as this week if outstanding issues were resolved.

The head of the Opel Trust, which was set up to stop Opel being dragged into GM's brief dip into bankruptcy, also urged a quick conclusion to the deal in comments on German radio earlier this week.

Under the deal -- which Magna wants to close within weeks of signing the contract -- GM is planning to sell a 55 percent stake in Opel to Canadian auto-parts manufacturer Magna and its partner, Russia's Sberbank. A European Commission spokesman said earlier this week that antitrust regulators have no plans to block the deal.

The Spanish unions also said that Magna had guaranteed that any offshoots of the Corsa, like the Tigra, would be manufactured there.

Magna's proposal was well received by the industry ministry and the Aragon regional government, the CCOO union said.

The planned job cuts at the Spanish plant will be reduced to a maximum of 900 from an original estimate of between 1,300 and 1,650, the unions said in a statement.

But unions from the Figueruelas plant will maintain their plans for four one-day strikes until the agreement with Magna has been ratified by members. The unions have called a meeting with Opel workers for Monday, when the plan will be presented and studied.

The strikes are due to take place on Oct. 28, Oct. 30, Nov. 3 and Nov. 5.

(Reporting by Judy MacInnes; Editing by Jon Loades-Carter and Rupert Winchester)