Italian workers at car-maker Fiat have held street rallies to keep the pressure on management, which has upped its bid to take over Opel.Throughout the week Fiat employees in Sicily held a series of strikes amid fears the merger would put their plant at risk. However Fiat’s chief executive, Sergio Marchionne, appears determined to out-do rival bidders who want to snap up Opel and the rest of General Motors’ European arm. Today Fiat made an improved and more detailed offer. That is likely to spark a counter offer from Fiat’s Austrian/Canadian bidding rival, Magna. The boss of the car-parts company, Siegfried Wolf, has said none of the four German Opel plants will close. He could not make any promises though for other GM plants in the UK and Belgium. Ultimately it is up to General Motors who it wants to sell to. But both Fiat and Magna, along with three other bidders, need to seduce the German government as Berlin will be providing billions of euros in loan guarantees.