In a preliminary assessment Thursday, the Australian Competition and Consumer Commission said the U.S. online travel agent's bid for Sydney-listed Wotif.com Holdings Ltd. could inflate commission rates charged to accommodation providers. The regulator is due to issue its final decision in October. Wotif shares slumped as much as 7% in Sydney on worries that the regulator will block the 703.1 million Australian dollar (US$657.1 million) deal. The ACCC often rejects deals for which it has expressed early reservations. By 0412 GMT, Wotif shares were down 4.3% at A$3.12, well below Expedia'sA$3.30 a share offer. "Market inquiries have indicated that Wotif is a major source of bookings for Australian accommodation providers and charges a lower commission rate than Expedia," ACCC Chairman Rod Sims said in a statement. Expedia and Wotif are two of Australia's three largest online travel agents, with the other being Priceline Group Inc. Get the full story at Nasdaq