* MSCI Latam stocks ~6%, FX ~3.5% stronger on the week * Chile c. bank mulled 150 bps rate hike at May meeting; peso +1% * Colombian leftist Petro holds lead in presidential race - poll * Rouble hits seven-year high vs euro on capital controls By Anisha Sircar and Bansari Mayur Kamdar May 20 (Reuters) - Latin American stocks leaped to a three-week high on Friday after China's moves to revitalize its ailing economy boosted investor confidence, while a gauge of currencies was headed for its first weekly gain in five as a dollar rally lost steam. China on Friday lowered the five-year loan prime rate by 15 basis points to 4.45%, while its securities regulator announced measures to support virus-hit sectors via capital markets, easing some fears around the impact of lockdowns and an economic slowdown. Iron ore prices surged 5.3% following a two-day slump, and copper prices gained on hopes of demand revival. "The fact that China is stepping up is a major boost for any Latin American country because their economies are going to be based off of the idea that the globalised system is revised," said Juan Perez, director of trading at Monex. Colombia's peso jumped 1.6%. Leftist presidential candidate Gustavo Petro, a former guerrilla vowing to tackle inequality, held a big lead ahead of the country's May 29 vote, a poll showed, though center-right rival Federico Gutierrez saw an uptick in support. "If polls go towards the more leftist candidate, there will be some risk aversion on the peso ... there's tremendous doubt about what types of reforms he would bring," Perez said. Brazil's real added 1% to also hit a three-week high, while Mexico's and Chile's peso were set for weekly gains. "Countries in Latam are probably close to the end of their hiking cycles given their early start, hence investors are biased to OW (overweight) duration in countries such as Brazil," Morgan Stanley strategist Min Dai wrote in a note. Chile's central bank considered raising rates by up to 150 basis points at its May meeting due to persistent inflation, central bank minutes showed. The currency has risen more than 4% since the decision after hovering at lows not seen since December. MSCI's index of Latam currencies tracked its first weekly gain in five as the dollar lost steam following its breakneck 10% surge, while stocks rose 6% this week. Elsewhere, Russia's rouble hit a seven-year high against the euro, which analysts attribute to EU countries preparing to pay Russia for gas and capital controls imposed by Moscow. Meanwhile, Turkey's central bank is likely to hold its policy rate at 14% next week despite an expected further rise in inflation after it hit 70% last month, a Reuters poll showed. Key Latin American stock indexes and currencies at 1500 GMT: Stock indexes Latest Daily % change MSCI Emerging Markets 1034.85 1.97 MSCI LatAm 2369.20 1.94 Brazil Bovespa 108481.24 1.38 Mexico IPC 51711.24 0.82 Chile IPSA 4984.04 0.04 Argentina MerVal 89670.41 1.169 Colombia COLCAP 1443.39 2.29 Currencies Latest Daily % change Brazil real 4.8643 1.11 Mexico peso 19.8790 0.22 Chile peso 832.9 0.48 Colombia peso 3994.85 1.32 Peru sol 3.725 0.24 Argentina peso 118.4900 -0.12 (interbank) Argentina peso 202 1.98 (parallel) (Reporting by Anisha Sircar in Bengaluru; Editing by Kirsten Donovan)