Germany's Siemens said on Tuesday it has decided to make an offer to French peer Alstom if it is given four weeks' time to do due diligence.

"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)