"The prerequisite for this offer is that Alstom agrees to give Siemens access to the company’s data room and permission to interview the management during a period of four weeks, to enable Siemens to carry out a suitable due diligence," said in a statement.
It said it had sent a letter to this effect to Alstom in the afternoon but gave no further details.
Siemens over the weekend approached Alstom with a proposal to exchange part of its train business plus cash for Alstom's power arm to counter a potential deal between Alstom and top rival General Electric.
(Reporting by Maria Sheahan; Editing by Madeline Chambers)