NEW YORK, Aug. 2, 2011 /PRNewswire/ -- ACI Worldwide, Inc. (Nasdaq: ACIW), a leading international provider of payment systems, today issued the following statement in response to the announcement by S1 Corporation (Nasdaq: SONE) that S1's Board of Directors rejected ACI's $9.50 per share cash and stock proposal: "Today's announcement from S1 does not change our strong belief that ACI's $9.50 per share cash and stock proposal is superior to the Fundtech transaction. ACI's proposal provides S1 shareholders with a substantial premium and immediate cash value for their investment in S1, as well as the opportunity to participate in the significant upside potential of ownership in a combined ACI-S1. "ACI remains ready and willing to complete this transaction, and we are prepared to do what is necessary to make this happen." As previously announced on July 26, 2011, ACI made a proposal to acquire all of the outstanding shares of S1 for $9.50 per share in cash and stock. ACI's proposal represents a 33% premium to S1's market price on July 25, 2011, the last trading day prior to the public announcement of ACI's proposal, a 32% premium to the volume weighted average price of S1 shares over the previous 90 days prior to the announcement, and a 23% premium to the 52-week high of S1 shares, for the 52-week period ending July 25, 2011. Under ACI's proposal, S1 shareholders could elect to receive cash and/or stock for their S1 shares, subject to proration such that in the aggregate 40% of the consideration is paid in ACI shares and 60% is paid in cash. ACI's proposal is structured so that the receipt of the stock portion of the consideration will be tax-free to S1 shareholders. ACI has secured committed financing from Wells Fargo Bank, N.A. for the cash portion of the transaction and anticipates that the proposed transaction could close as early as the fourth quarter.