Germany could send a negotiation team to the United States at the end of the week to discuss solutions for General Motors unit Opel, Economy Minister Karl-Theodor zu Guttenberg said on Monday.

Guttenberg has said Germany is discussing plans with U.S. partners about a trustee arrangement if GM were to file for bankruptcy before a deal had been reached on a partner for Opel. The trustee idea has met some resistance in the United States.

(I'm) optimistic in principle, Guttenberg told reporters in Munich, referring to talks on the trustee idea.

The German government has made finding offers by investors a precondition for a trustee arrangement and has given interested parties until Wednesday to submit their offers for the carmaker.

Sources have told Reuters that Italian carmaker Fiat , Austrian-Canadian car parts maker Magna as well as private equity firm RHJ have had access to Opel's books. However, it was not clear whether U.S. private equity firm Ripplewood's European arm RHJ would decide to bid as well, the sources said.

Guttenberg said he expected offers from Fiat and Magna, but did not say whether there were other interested parties.

We have to see what happens on Wednesday, he said.

Fiat wants a three-way merger with Chrysler and GM's European operations. Magna is also interested in Opel, probably together with Russian investors.

Guttenberg said on the weekend Opel could go bankrupt if the competing business plans for the carmaker from Fiat and Magna were both unsuitable.

The German government has outlined an idea whereby a trustee could protect Opel assets from GM creditors while a consortium of banks could provide Opel with bridge financing, until another investor takes it over.

(Reporting by Irene Preisinger; Writing by Kerstin Gehmlich; Editing by Jon Loades-Carter)