* Latam currencies fall on dollar buying * Colombian peso hit by weak c.bank outlook By Ambar Warrick Feb 4 (Reuters) - Mexico"s peso led early losses across Latin American currencies on Thursday after the Supreme Court struck down a key component of the government"s reform agenda, while most other units fell on increased buying into the dollar. The peso dropped 0.6% to the dollar after Mexico"s Supreme Court upheld an antitrust suit 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. "The DXY index is on track to register its fourth day of gains out of the last five... This comes even though global equities have been able to shake off some weakness overnight and return to a positive trajectory," analysts at TD Securities wrote in a note. Chile"s peso was also among the worst performers in Latam on Thursday, as concerns over a near-term drop in Chinese demand weighed on the prices of copper, the country"s top export. The peso has been subdued despite the launch of a COVID-19 vaccination program this week. Most Latam currencies have lagged their broader emerging market peers this year as a second wave of COVID infections damaged economic activity and raised concerns over stretched fiscal spending in the region. Colombia"s peso dropped 0.5% after the 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. Most Latam stocks rose in early trade, tracking overnight gains on Wall Street. Brazilian iron ore miner Vale SA pushed up the Bovespa index after it forecast a strong production ramp-up in 2021, as well as improved sales. Key Latin American stock indexes and currencies: Latest Daily % change MSCI Emerging Markets 1388.66 -0.29 MSCI LatAm 2382.54 -0.32 Brazil Bovespa 120058.32 0.28 Mexico IPC - - Chile IPSA 4402.82 0.02 Argentina MerVal 50429.92 1.148 Colombia COLCAP 1363.83 0.35 Currencies Latest Daily % change Brazil real 5.3803 -0.22 Mexico peso 20.3120 -0.63 Chile peso 736.4 -0.43 Colombia peso 3550.86 -0.48 Peru sol 3.6447 -0.11 Argentina peso 87.9000 -0.10 (interbank) (Reporting by Ambar Warrick in Bengaluru; Editing by Bernadette Baum)