The media group's move comes after government pressure on Dailymotion owner Orange to keep the Youtube competitor in French hands.
Former French president used Facebook to declare his bid to become head of the opposition UMP party, ahead of presidential elections in 2017.
The move by Alain Juppé, 69, has upstaged an expected imminent similar bid by Nicolas Sarkozy to run as the UMP party's 2017 candidate.
The US giant has finally won its lengthy bidding against rivals after shareholder Bouygues agreed to sell its stake to the French government.
The race of rival bids for French engineering firm's energy arm appeared over as French government backs that of General Electric.
GE's chief executive tells French president his firm would create 1,000 jobs over three years if its bid for Alstom's energy division is approved.
The US company, bidding for Alstom's energy arm, said it would satisfy French government's demand that nuclear unit remain in France.
No binding decision on GE's bid for Alstom's energy division will be made before end of May, giving Siemens time to renew a counter offer.
France's economy minister says Siemens bid for the troubled French engineering firm would create “two European champions”.
Siemens is reportedly mulling an offer for the troubled French firm, just as General Electric's CEO travels to Paris for talks on its own bid.