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By Guillermo Parra-Bernal and Tatiana Bautzer
SAO PAULO, April 6 (Reuters) - Cetip SA Mercados Organizados , Brazil's biggest securities clearinghouse, has agreed on most terms of a revamped, unsolicited offer by bourse BM&FBovespa SA, a source with direct knowledge of the matter said on Wednesday.
The boards of both companies, which are based in São Paulo, were expected to give their blessing to the deal within the "next 48 hours," said the source, who requested anonymity because the process is under way.
Following months of rumors and a failed preliminary bid, Cetip rejected an unsolicited offer worth 10.8 billion reais ($2.9 billion) from BM&FBovespa on March 2, but authorized financial advisers to pursue an improved deal.
A takeover will make BM&FBovespa the dominant exchange in Brazil, controlling depositary and clearing activities for all types of financial assets and sourcing investors with proprietary market data. Cetip is Latin America's largest depositary of financial securities with a vast over-the-counter, fixed-income derivatives operation.
Shares in BM&FBovespa accelerated losses after the Reuters report, closing 4.2 percent down at 14.97 reais. Cetip gained 1.3 percent to 41.17 reais, above the 41 real-a-share bid that BM&FBovespa made in February.
O Estado de S. Paulo newspaper reported the combination earlier on Wednesday, without citing how it obtained the information. The resulting company from the takeover will create a giant with about 40 billion reais in market capitalization.
Both Cetip and BM&FBovespa declined to comment.
The negotiations came after years of speculation that BM&FBovespa could pursue an unsolicited takeover of Cetip to grow in registration and custody of fixed-income and credit market instruments, segments in which the bourse has failed to gain market share.
According to Carlos Gómez-López, an analyst with HSBC Securities in New York, a recent rally in Brazilian stocks and the currency made the most recent BM&FBovespa takeover proposal "more attractive for Cetip shareholders." He said that, under such a proposal, they would receive 75 percent of the amount offered in cash. ($1 = 3.6699 Brazilian reais) (Editing by Chris Reese and Jonathan Oatis)