* Latam currencies fall on dollar buying * Colombian peso hit by weak central bank outlook (Updates prices, adds market details) By Ambar Warrick and Susan Mathew Feb 4 (Reuters) - Brazil"s real led losses across Latin American currencies on Thursday, and Mexico"s peso fell 1% after the Supreme Court struck down a key component of the government"s reform agenda. The real dropped 1.4% as fiscal worries outweighed stimulus hopes and optimism that the government"s reform agenda was likely back on track after allies of President Jair Bolsonaro were elected this week to head the Congress. "The main uncertainty at this point is whether the government will be able to accommodate (fiscal support) under the spending cap," wrote Citi group strategists in a note. "The most likely scenario is public spending surpassing the limit ... this year by 1 percentage point of GDP. "With that said, in the short-run, we expect Brazilian assets to be buoyed by the aligned speeches between the new Congress leadership and the government," they said. Mexico"s peso dropped 0.6% to the dollar after the country"s Supreme Court upheld an antitrust lawsuit against a crucial part of the government"s plan to reform the power sector. The move would have given state-run electricity generators an edge in the sector, and was met with criticism from private businesses. Other Latin American currencies fell as positive U.S. economic data and optimism over a bumper stimulus package drove buying into the dollar, despite its position as a currency that usually weakens during risk-on trade. Crude exporter Colombia"s peso weakened despite rising oil prices. The government"s plan to vaccinate over 35 million people against the coronavirus this year could face delays, President Ivan Duque said on Wednesday. Meanwhile, Colombia appointed Viviana Taboada and Mauricio Villamizar to the central bank"s board amid debate among policymakers about whether to continue low interest rates or guard against possible future inflation upticks. "The appointments have generated criticism and could imply a mildly dovish shift, if there is a shift at all. Both appointees are relatively young and not very well known locally. This has generated a stir locally since some more experienced economists were overlooked," Citi group strategists said. Most Latam currencies have lagged their broader emerging market peers this year as a second wave of COVID-19 infections damaged economic activity and raised concerns over stretched fiscal spending in the region. Colombia"s central bank said that the second wave of infections - which had spurred tighter restrictions in major cities - will affect the country"s economy throughout the remainder of 2021 and delay its recovery. Key Latin American stock indexes and currencies: Stock indexes Latest Daily % change MSCI Emerging Markets 1387.08 -0.4 MSCI LatAm 2363.88 -1.1 Brazil Bovespa 119315.09 -0.34 Mexico IPC 44235.88 0.63 Chile IPSA 4412.40 0.24 Argentina MerVal 50357.10 1.002 Colombia COLCAP 1355.99 -0.22 Currencies Latest Daily % change Brazil real 5.4460 -1.43 Mexico peso 20.4100 -1.10 Chile peso 736.6 -0.46 Colombia peso 3556.44 -0.64 Peru sol 3.6428 -0.06 Argentina peso 87.9100 -0.11 (interbank) (Reporting by Ambar Warrick and Susan Mathew in Bengaluru; Editing by Bernadette Baum and Matthew Lewis)