* Copper boosted by planned labor strikes at Chile mines * Mexican economy grew more in Q1 than first estimated * Brazil"s Gol rises, says domestic air travel outlook improving (Adds comments, bullets, details; Updates prices throughout) By Susan Mathew and Shreyashi Sanyal May 26 (Reuters) - Chile"s peso rebounded on Wednesday from a two-day decline as copper prices rose on a planned labor strike at the world"s biggest copper mine, while stronger economic growth in Mexico supported its peso. The Chilean currency added 0.5% against the dollar after a union representing workers at BHP Group"s Escondida and Spence copper mines rejected the company"s contract offer and urged members to walk off the job from Thursday, threatening already low global supplies of the red metal. "Copper-producing countries are likely to increase taxation on miners, with Chile having already proposed substantially higher royalties," analysts at Deutsche Bank wrote in a client note. MSCI"s index of EM currencies dipped 0.1%, while Mexico"s peso rose 0.2% to 19.880 per dollar. Data released on Wednesday showed Mexico"s economy grew faster in the first quarter than earlier estimated as the country slowly recovers from its sharpest contraction since the 1930s. "We estimate a better performance of GDP from (the second quarter onwards), mainly driven by the expansion of the U.S. economy, as domestic demand should remain on a more gradual recovery trend; we thus maintain our 2021 GDP growth forecast at 5.1%," said strategists at Citi Research. The upcoming midterm elections in Mexico may cause "noise" but the peso exchange rate was expected to remain stable in the range of 19.9 to 20.1 to the dollar, Mexican Deputy Finance Minister Gabriel Yorio said on Tuesday. Brazil"s real rose 0.5%. Late on Tuesday, Brazil"s Economy Minister said the local economy might grow by as much 5% this year. The real is down almost 2.3% this year, with concerns about fiscal spending being one of the main factors weighing on sentiment. Meanwhile, a Reuters poll showed Brazil"s equity market is on course for its second slowest year since 2015 as the coronavirus pandemic continues unabated in Latin America"s biggest economy. Sao Paulo"s benchmark equity index was up 0.6%, with airline Gol rising 6% after it cited an improvement in May domestic ticket sales, driven by advances in Brazil"s COVID-19 vaccination program. Smaller rival Azul SA topped the index. A source told Reuters Azul had approached Chile"s bankrupt LATAM Airlines Group with the aim of buying its Brazilian operation. Peru"s sol fell 0.8% to a new low with less than two weeks to go before a second round of presidential elections. Recent polls show front-runner and socialist Pedro Castillo with a growing lead over business-friendly conservative Keiko Fujimori. Colombia"s peso eased its fall as oil prices steadied, while the stock index was flat with oil major Ecopetrol hitting three-week lows. Ecopetrol on Wednesday said social unrest in Colombia over tax reforms had adversely impacted its operations. Key Latin American stock indexes and currencies at 1914 GMT: Stock indexes Latest Daily % change MSCI Emerging Markets 1352.36 0.51 MSCI LatAm 2470.75 0.71 Brazil Bovespa 123750.95 0.62 Mexico IPC 49123.21 0.61 Chile IPSA 4099.85 0.22 Argentina MerVal 56426.07 0.363 Colombia COLCAP 1190.99 -1.06 Currencies Latest Daily % change Brazil real 5.3122 0.47 Mexico peso 19.8800 0.17 Chile peso 729.1 0.66 Colombia peso 3740.75 -0.09 Peru sol 3.8528 -0.83 Argentina peso (interbank) 94.4800 -0.21 Argentina peso (parallel) 152 0.66 (Reporting by Susan Mathew and Shreyashi Sanyal in Bengaluru; Editing by Jane Merriman and Richard Chang)