While GE has already made a formal bid for the company's energy business, Siemens has joined the fray later.
It said in a statement today that its board has "decided to make an offer to Alstom" but as a prerequisite it needs "access to the company's data room and permission to interview the management during a period of four weeks".
Siemens said it has submitted a letter to Alstom in this regard and has not yet received a response.
The two companies stepped up their efforts to take control of Alstom's power business on Monday, with Siemens confirming that it sent it CEO to France to meet the president.
Following this meeting, Siemens said it would "convene as soon as possible to decide whether to make an offer for Alstom and what this will consist of". GE's CEO has already met with French President Francois Hollande to discuss the company's planned takeover of Alstom Power.
GE will be keen to allay the fears over the takeover of a major French firm by an American rival. The French government has expressed concern about GE's bid to buy all or part of the French manufacturer, which is a major player in the global wind industry, for a reputed $13 billion.
As such, it has encouraged a European counterbid, with Siemens stepping in and expressing interest in taking on Alstom's power business in return for part of its train-manufacturing division as well as cash.
The move would see Siemens take control of Alstom's wind business, which has installed 2,600 wind turbines across more than 200 wind farms, with a capacity of around 5GW.
Alstom is also a direct competitor of Siemens in the offshore wind market, with its 6MW Haliade turbine filling a similar space to Siemens' 6MW machine.
French economy minister Arnaud Montebourg has been pushing for an alternative to the GE bid, telling reporters on Friday that the government "is expressing its patriotic concern and vigilance".
Alstom shares remain suspended on the French stock exchange as speculation swirls around the possibility of a takeover.
Either move to buy the company would be bound to have significant consequences for the wind industry. Both bidders are major players in wind, and an acquisition would mean consolidation and the removal of a competitor from the market.