* Chile's peso set for biggest-ever monthly gains * Other Latam currencies trading flat * Global sentiment remains optimistic * Brazil shares dip from record highs By Sagarika Jaisinghani and Ambar Warrick Dec 20 (Reuters) - The Chilean peso gained on Friday as senators approved a referendum on changing the country's dictatorship-era constitution next year, while other Latin American currencies were near flat as traders settled in for the holidays. The peso rose as much as 1% as Congress approved the plan to ask voters whether the country needed a new constitution, a central demand of protests that have brought the country to a near standstill since October and battered the currency. Friday's gains added to an improvement in global outlook this week and put the peso on track for its biggest-ever monthly increase. A basket of Latin American currencies was also on course to finish the year on a strong note, as the United States struck back-to-back deals with some of its most important trading partners: China, Mexico and Canada. But with a U.S.-China trade deal not yet formally signed and British Prime Minister Boris Johnson's hard line on Brexit negotiations, analysts said there was little motivation for assets in the developing world to keep up their recent run. "The EM rally is running out of steam a bit," said Win Thin, head of emerging market currency strategy at Brown Brothers Harriman. "Between the year end, and some uncertainty ahead, it's very quiet at our trading desk." The Brazilian real was nearly flat, shrugging off a better-than-expected increase in the IPCA-15 consumer price index, considered the official inflation forecast for Latin America's biggest economy. Mexico's peso gained slightly for the second day in a row. On Thursday, the central bank cut its benchmark interest rate for the fourth consecutive time, as expected. In equities trading, Brazilian shares dipped from record highs, with the biggest domestic airline, Gol Linhas Aereas Inteligentes SA, shedding about 1.2%. The company said it would boost standard ticket prices sold to its loyalty program Smiles Fidelidade SA by 41%. Smiles' shares fell 1.3%. Chile's stock index was down about 0.4%, while Argentina's MerVal added 1%. Key Latin American stock indexes and currencies at 1438 GMT: Stock indexes Latest Daily % change MSCI Emerging Markets 1107.80 0.11 MSCI LatAm 2897.67 -0.38 Brazil Bovespa 114669.91 -0.4 Mexico IPC - - Chile SPIPSA 4735.13 -0.37 Argentina MerVal 38515.07 1.135 Colombia Colcap 1642.99 -0.23 Currencies Latest Daily % change Brazil real 4.0746 -0.31 Mexico peso 18.8908 0.12 Chile peso 747.8 0.80 Colombia peso 3317.78 -0.20 Peru sol 3.3238 0.25 Argentina peso (interbank) 59.8200 - (Reporting by Sagarika Jaisinghani in Bengaluru; Editing by Dan Grebler)
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