June 18 (Reuters) - Brookfield Infrastructure Partners (BIP.N) on Friday revised its buyout offer for Inter Pipeline Ltd (IPL.TO) to include an option for an all-cash consideration, instead of a mix of cash and stock. Brookfield"s revision comes as the investment firm tries to beat a rival bid from Pembina Pipeline Corp (PPL.TO), which has been recommended by Inter"s board. Pembina has an all-stock bid of about C$8.3 billion ($6.71 billion), while Brookfield had offered C$8.48 billion with 74% cash. On Friday, Brookfield said Inter shareholders may now elect to get C$19.50 in all cash per Inter share, or 0.225 of Brookfield"s class A share, valued at C$19.99 per Inter share as of Thursday"s close. Brookfield also said it was prepared to raise its offer by up to C$0.901 per Inter share, to C$20.401 per Inter share, pending the outcome of its challenge before the Alberta securities regulator. The company last week filed an application with the regulator to do away with Inter"s C$350 million termination fee to Pembina, saying it would increase its takeover offer for Inter if the fee was reduced or eliminated. ($1 = 1.2363 Canadian dollars) Reporting by Arathy S Nair in Bengaluru; Our Standards: The Thomson Reuters Trust Principles.