Chicago Mercantile Exchange Holdings Inc. is expected to sweeten its bid for CBOT Holdings Inc., the Wall Street Journal reported on Friday.

Under the new bid, CME would offer CBOT shareholders 36.2 percent of a combined company, up from 34.6 percent before, the paper reported.

The move is a sign the CME is feeling pressure from IntercontinentalExchange Inc.'s (ICE.N: Quote, Profile, Research) unsolicited bid for the CBOT. CME shareholders and CBOT shareholders are separately scheduled to vote on a tie-up on Monday.