Read MoreImmelt rebuffs notion Alstom deal a 's--- show'
This reflects that Siemens would be transferring its trains business to Alstom, allowing the French government to trumpet the creation of a new European rail champion.
It also follows a decision by Siemens to exclude some Alstom energy activities— nuclear, wind energy, and transmission and distribution (T&D)—from its bid, two sources said.
Both Siemens and Alstom declined to comment.
Alstom is already in talks with GE over a 12.35 billion euro ($16.8 billion) all-cash offer for its power arm, which has been extended until June 23. Under strong political pressure, it has opened its books to Siemens so the German firm can propose its own deal if it wants to.
Read MoreFrench govt gets more time to weigh GE/Alstom deal
Excluding Alstom's nuclear and wind businesses from its bid could allow the the French group to sell them directly to state-controlled energy firm Areva. But it could also create problems as one source close to the French camp said it would be difficult to separate the nuclear side of the turbine business from non-nuclear activities.
As for the T&D business, valued at 1.5 to 2 billion euros, sources said Siemens was worried that acquiring Alstom's assets in this area would create formidable regulatory hurdles given the dominant position Siemens already enjoys in the sector.
Therefore, the German firm has decided to also exclude T&D— a business that makes technology for transporting electricity from power plants to consumers—from its offer.
As previously reported by Reuters, Siemens would be offering its rail activities and would propose creating a joint venture with Alstom in rail signalling.
One source said Siemens was keen to retain a controlling stake in any signalling venture, potentially another source of conflict as Alstom is also seen eager to have a majority share. How the signalling stakes are divided up would affect the cash component of the Siemens bid, the source added.
Sources said the offer also reflected a deduction of up to 800 million euros to cover potential compliance risks that Alstom's power unit faces in the United States, United Kingdom and Brazil.
While Siemens could present the formal offer for Alstom's power arm as early as Wednesday of this week, one of the sources said the German group may decide to take some extra time after GE extended its bid until June 23 at the request of the French government.