* Mexican peso on track for worst day in nearly a month * U.S. inflation spikes, risk assets under pressure * Brazil"s service sector activity surges in May (Updates prices) By Ambar Warrick and Susan Mathew July 13 (Reuters) - Mexico"s peso lost 1% on Tuesday on concerns over more government interference in the energy sector, while most other Latin American currencies fell as rising U.S. inflation raised fears of monetary policy tightening by the Federal Reserve. Mexican President Andres Manuel Lopez Obrador said he plans to send a constitutional reform to Congress, widely opposed by independent power firms and investors on grounds that it would hurt competition. Given the president"s majority in the Senate and Lower House have been reduced after mid-term elections last month, a consensus with the opposition could be difficult to reach, Citi strategists said in a note, signaling more uncertainty. The Mexican peso dropped as much as 1.1%, heading for its worst day in nearly a month. 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, meanwhile, erased losses as the session progressed. Market experts remain fairly constructive on the real to the year-end given economic growth in the country has been wholly positive this year. But they warn of political risks. Data on Tuesday showed services activity in Brazil grew 23.0% in May from last year. Most other currencies fell as the dollar rallied after data showed U.S. consumer prices shot up at their highest rate in 13 years in June. 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. Chile"s peso lost 0.9% with a slide in prices of the country"s biggest export, copper, on declining China imports, bolstering losses. Peru"s sol inched closer to all-time lows, while Colombia"s peso slipped marginally. 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. Among stocks, Brazilian shares rose 0.6%, bucking gloom in other regional benchmarks. Pharmaceutical company Hypera topped Brazil"s index after it said it acquired 12 over-the-counter and prescription brands in Latam from France"s Sanofi for $190.3 million. Key Latin American stock indexes and currencies: Stock indexes Latest Daily % change MSCI Emerging Markets 1337.76 0.82 MSCI LatAm 2567.83 0.44 Brazil Bovespa 128352.97 0.59 Mexico IPC 49368.13 -0.85 Chile IPSA 4185.60 -1.36 Argentina MerVal 64138.64 -0.119 Colombia COLCAP 1292.89 -0.43 Currencies Latest Daily % change Brazil real 5.1704 0.05 Mexico peso 20.0467 -1.00 Chile peso 749.4 -0.88 Colombia peso 3819.2 -0.03 Peru sol 3.976 -0.56 Argentina peso 96.1200 -0.02 (interbank) (Reporting by Ambar Warrick; Editing by Paul Simao and Dan Grebler) Our Standards: The Thomson Reuters Trust Principles.