Fiat (FIA.MI) is discussing closing one of its plants in Italy and reducing operations at another, German unions have told their Italian counterparts, an official of Italy's FIM-CISL union told Reuters on Wednesday.

We are very worried because, according to the Germans, Fiat is talking about downsizing Pomigliano (plant) and about the schedule for closing Termini Imerese, Bruno Vitali said.

He was speaking after a meeting in Frankfurt with German unions as Fiat seeks to merge its operations in Europe with GM's (GM.N) Opel unit.

Italian unions have said that Fiat's ambitious plan to create the world's second-biggest car maker is positive even though they are concerned about plant closures and job losses.

They have called for a meeting with the Italian government and the company. Industry Minister Claudio Scajola said he would meet all the parties at the right moment, adding he was in continuous contact with Fiat.

German unions, who have previously expressed willingness to dig into their own pockets to help Opel, fear they will bear the brunt of plant closures and job losses. Some have come out in favor of a rival bid by Magna International Inc (MGa.TO), an Austrian-Canadian car parts maker.

Fiat has already agreed to take a 20 percent stake in U.S. car maker Chrysler LLC CBS.UL alongside U.S. unions which will have a 55 percent stake in the combined group.

The Italian car maker would bring its expertise in building smaller, more environmentally-friendly cars to the deal with Chrysler -- but these vehicles would clearly overlap with Opel models in Europe.

Fiat's share of the market in the 15 main European countries in April is likely to be 9.9 percent, according to figures released on Wednesday by forecaster Global Insight, up from 9.2 percent in March.