Siemens is working on a formal asset-swap offer for Alstom's power business that could come as early as this week, sources close to the talks have said.
The deal could also see France take a stake in a resulting rail-focused French group, though some sources familiar with the talks told Reuters there was doubt over whether Alstom would be interested in the new deal sketched out by Siemens.
Alstom is already in talks with US conglomerate General Electric (GE) over a €12.35bn (£10bn) bid for its power arm, which it is due to review by June 2, but under strong political pressure from the French Government it has opened its books to Siemens so it can propose its own deal if it wants to.
The French government has repeatedly criticised GE's bid, favouring alliance between the companies rather than a straight sale of Alstom's power arm – which accounts for 70 per cent of the group's revenue – that would leave the French group with just its smaller transport business.
A rival offer would give the French government more leverage with GE after it gave itself the power to block foreign takeovers in "strategic sectors". It has advocated an alternative European tie-up between Alstom and Siemens, though initially it faced reluctance from both firms, long bitter rivals.
But after several trips to Paris by CEO Joe Kaeser and nearly two weeks of access to Alstom's data, Siemens has warmed to the idea and has been refining its bid to make it more attractive to Alstom and the French government, sources said.
"Siemens is presenting the following case: it will create national champions in trains and energy. Everything will be kept in Europe. It has offered some new elements, which sweeten its proposal," a source familiar with the proposed deal told Reuters.
In a short letter to Alstom late last month, Siemens had outlined a proposal worth $14.5bn (£8.6bn), offering to exchange part of its rail business plus cash in exchange for Alstom's power assets. Two sources familiar with the talks said Siemens was now discussing handing over all of its rail business to Alstom and setting up a joint-venture in rail signalling.
To limit the German firm's influence in the resulting transport-focused Alstom group, Siemens is also discussing with Paris and Berlin the opportunity for France – which owns 0.9 per cent of Alstom's capital via state fund CDC – to take a more sizeable stake, political and financial sources said.
One source said the French government could take a stake of over 10 per cent in Alstom, as it seeks to secure the domestic roots of the engineering group which received a state bailout a decade ago and is a big private employer in the country.
On Friday, French Economy Minister Arnaud Montebourg said the government would not let domestic companies be "dismembered, chopped up into pieces and devoured" and did not rule out taking a stake in Alstom to help secure its future.
Meanwhile Siemens could offer to sell Alstom's wind and nuclear power assets to French state-controlled energy group Areva, thereby addressing government concerns over France's energy independence, said two sources familiar with the proposed deal.
As a further sweetener, Siemens is said to be offering to set up in France the headquarters of sub-units in Transmission and Distribution – the segment which makes gear to carry electricity from power plants to households – potentially strengthening the country as a hub for this technology.
Siemens declined to comment. It has previously said it plans to use the full four weeks allotted to it for due diligence, and then decide on whether to make a formal offer.
Alstom declined to comment beyond saying it was reviewing GE's bid and had received an expression of interest from Siemens, but no formal offer. General Electric and Areva also declined to comment.