* Finmeccanica selling AnsaldoEnergia unit
* Three Italian suitors for state-backed FSI fund bid-source
* Shares close up 3.2 percent, outperform weak market
MILAN, Oct 2 (Reuters) - Italy's Industry Minister Corrado Passera would prefer an Italian bid for the AnsaldoEnergia unit that Finmeccanica SpA has put on the block to restructure its business.
Germany's Siemens AG , Europe's biggest engineering group, emerged last week as favourite to buy AnsaldoEnergia, whose disposal is vital for the turnaround of Italy's No.2 industrial group.
The possibility of a Siemens bid prompted state-backed Fondo Strategico Italiano (FSI) to send a rival expression of interest for the company, two sources close to the matter said on Monday.
"All remains to be seen. But it's clear that whenever there is a possibility of having Italian businessmen investing in Italy, this is a preferable solution," Passera told reporters on Tuesday on the sidelines of an event.
The sale of AnsaldoEnergia, a power engineering company with a strong presence in North Africa, could become the first major disposal for Finmeccanica Chairman Giuseppe Orsi, who is under pressure from a corruption probe and has promised to sell assets worth 1 billion euros by the end of the year.
An offer from FSI for the 55 percent Finmeccanica owns in AnsaldoEnergia would be made together with three Italian groups, a trade union source said on Tuesday.
U.S. fund First Reserve owns the remaining 45 percent.
AnsaldoEnergia's top management may back an Italian offer by taking a "symbolic" stake, a person familiar with the situation told Reuters.
Siemens could table a 1.3 billion euro ($1.7 billion) offer for the Genoa-based company, two bankers familiar with the German conglomerate's strategy said in July.
Shares in Finmeccanica closed up 3.2 percent at 4.01 euros, outperforming a weaker market. ($1 = 0.7731 euros)
(Reporting by Sara Rossi and Danilo Masoni; Editing by David Holmes)
Keywords: FINMECCANICA ANSALDO/