* Hitachi exec calls Mitsubishi Heavy-Siemens joint bid 'great news'
* Nikkei says three-way bid would be worth $9.8 bln, exclude power grid
* Mitsubishi Heavy, Hitachi have combined their thermal power operations (Updates with confirmation by Hitachi executive; 1 trillion yen deal value in Nikkei report)
TOKYO, June 12 (Reuters) - Hitachi Ltd said it hopes to join Mitsubishi Heavy Industries Ltd and Siemens AG in their joint bid for Alstom SA's energy assets, which the Nikkei newspaper said would be worth 1 trillion yen ($9.80 billion).
A three-party bid would give the group greater financial firepower and flexibility to counter a rival $17 billion bid for the French company's power business by General Electric Co .
Hitachi and Mitsubishi Heavy are no strangers to each other. They merged their thermal power businesses at the start of this year.
"Mitsubishi Heavy is our partner. We want to work together with them," Katsumi Nagasawa, head of Hitachi's power systems group, told a briefing on Hitachi's business on Thursday. He said the joint Siemens-Mitsubishi Heavy bid was "great news".
The Nikkei said earlier on Thursday that the two Japanese companies would set up a joint venture to bid for Alstom's steam turbine operations, which it said would be valued at 500 billion yen ($4.90 billion).
Mitsubishi Heavy would hold 65 percent and Hitachi 35 percent of the venture, matching the shareholdings in their existing thermal power partnership, the paper added.
Siemens is expected to offer 500 billion yen for Alstom's gas turbine business, while Alstom's power grid business would be excluded from the deal, the Nikkei said. ($1 = 102.0500 Japanese Yen) (Reporting by Reiji Murai; Writing by Edmund Klamann; Editing by Chris Gallagher and Ryan Woo)