UPDATE 2-Magna discusses Opel offer with German government

* German EconMin says Magna presents outlines of Opel offer

* Magna seeks control of Opel-German politician Beck

* Magna working alongside third-party investor-source

(Adds details on the outlines of a potential Magna deal)

BERLIN/FRANKFURT, April 28 (Reuters) - Austrian-Canadian car parts maker Magna (MGa.TO: Quote, Profile, Research) has presented the rough outlines of a rival offer to seize control of General Motors' GM.N Opel unit ahead of Italy's Fiat (FIA.MI: Quote, Profile, Research), German Economy Minister Karl-Theodor zu Guttenberg said.

Magna's approach marks an effort to elbow aside Italy's Fiat as politicians and investors grapple to find a long-term solution for Germany-based Opel.

Magna is seeking control by working together with a third-party investor, a person familiar with Magna's thinking told Reuters.

A spokesman for the office of Kurt Beck, state premier of Rhineland-Palatinate on Tuesday said Magna wanted to buy a 20 percent stake in Opel but was seeking control through direct and indirect stakes.

Rhineland-Palatinate is one of four German states where Opel plants are located. Magna declined to comment on details of its proposal outline.