The operator of the Frankfurt stock exchange is preparing to file an offer document with German regulator BaFin as early as Tuesday, the people said.
Deutsche Boerse declined to comment.
On Sunday, NYSE Euronext's board of directors unanimously rejected the rival $11.3 billion offer from Nasdaq OMX Group
At current share price levels Deutsche Boerse's offer is worth $10 billion, less than the Nasdaq/ICE offer.
(Reporting by Edward Taylor; Writing by Maria Sheahan)