* Mexican peso eyes worst day in nearly a month, down 1% * U.S. inflation spikes, risk assets under pressure * Brazil"s service sector activity surges in May By Ambar Warrick July 13 (Reuters) - Latin American currencies came under pressure from a spike in U.S. inflation on Tuesday as investors feared monetary policy tightening by the Federal Reserve, while Mexico"s peso tumbled on concerns over more government interference in the energy sector. MSCI"s index of Latin American currencies fell 0.1% in early trade after data showed U.S. consumer prices shot up at their highest rate in 13 years in June. The dollar and Treasury yields both rose after the data. A sustained spike in inflation could push prices above the Fed"s target inflation range, and compel the U.S. central bank to tighten policy earlier than anticipated. "It came in very hot, much hotter, so it is going to be difficult for the Fed or any of the talking heads to try to talk it away as transitory ... it is significantly stronger, and that plays right into the ongoing inflationary concerns," said Ken Polcari, managing partner at Kace Capital Advisors. Mexico"s peso led the losses across Latin America, sinking as much as 1% and eyeing its worst day in nearly a month. Mexican President Andres Manuel Lopez Obrador said he plans to send a constitutional reform to Congress to protect public-sector interests over private companies in the electricity market. Lopez Obrador"s stance on the country"s energy market has been widely opposed by independent power firms and investors on the grounds that it would hurt competition. Recent volatility in the oil market also weighed on the peso. The International Energy Agency warned that while the oil market could see tighter supply due to an OPEC+ dispute, there remains a risk of a dash for market share. Brazil"s real fell 0.2%, now on track to lose ground in nine of the past 10 sessions as corruption scandals in Latin America"s largest economy sapped appetite for the currency. Waning iron ore imports in China, the largest exporter of the steelmaking ingredient from Brazil, could also hurt the real this year. But economic growth in Brazil has been wholly positive this year, as more of the country emerges from COVID-19 lockdowns. Data on Tuesday showed services activity in Brazil grew 23.0% in May from last year. In an update to Argentina"s debt woes, the International Monetary Fund said progress was being made in talks over the roughly $45 billion owed to the Fund. Broader emerging market currencies also retreated after the U.S. inflation data, with MSCI"s index falling 0.1%. Latin American stocks fell in early trade, tracking losses on Wall Street. Key Latin American stock indexes and currencies: Latest Daily % change MSCI Emerging Markets 1338.11 0.85 MSCI LatAm 2556.97 0.01 Brazil Bovespa 127194.78 -0.31 Mexico IPC 49890.80 0.2 Chile IPSA 4209.63 -0.79 Argentina MerVal - - Colombia COLCAP 1297.41 -0.08 Currencies Latest Daily % change Brazil real 5.1829 -0.19 Mexico peso 19.9908 -0.73 Chile peso 744.28 -0.15 Colombia peso 3821.51 -0.09 Peru sol 3.9605 -0.17 Argentina peso 96.1200 -0.02 (interbank) (Reporting by Ambar Warrick Editing by Paul Simao) Our Standards: The Thomson Reuters Trust Principles.