By Nelson Renteria and Michael O'Boyle SAN SALVADOR, Feb 2 (Reuters) - A former left-wing guerrilla commander had a strong lead in El Salvador's presidential election on Sunday and heads into a run-off vote well positioned to defeat a conservative rival who wants to fight powerful street gangs with the army. Salvador Sanchez Ceren, who became a top leader of the now-ruling leftist Farabundo Marti National Liberation Front (FMLN) during El Salvador's civil war, had 49 percent support with votes in from more than 94 percent of polling booths. His right-wing opponent, former San Salvador Mayor Norman Quijano, had 38.9 percent of the vote. Sanchez Ceren had needed 50 percent to avoid a run-off on March 9 but with a 10-point lead over Quijano he was optimistic. "We won the first round ... we are sure that in the second round we will win by more than 10 points," he told cheering supporters. "It a great victory for the people of El Salvador." The FMLN turned into a political party at the end of the civil war in 1992 and it took power at the last election in 2009 after softening some of its hard-left policies. Still, Sanchez Ceren's campaign was helped by the FMLN government's mix of popular welfare programs, including pensions and free school supplies. "The Front is going to win because of the poor. They are giving us opportunities. My kids would not have been able to study without their help," said housewife Patricia Concepcion, 43, as voting wrapped up. The third-place candidate Antonio Saca, who was president from 2004 until 2009, had about 11.4 percent support. After he left office, Saca broke away from Quijano's Nationalist Republican Alliance (Arena) party. The Universidad Centroamericana estimates that while about 60 percent of Saca's supporters would likely opt for Quijano in the run-off, around 25 percent would go with Sanchez Ceren. That would be enough to give him a clear win. A victory for the FMLN would also boost the influence of Venezuela's socialist government in Latin America, as Sanchez Ceren has said he would seek to join the South American oil giant's Petrocaribe oil bloc, which furnishes mainly leftist allies with cheap energy. GANGS El Salvador's sluggish economy is heavily reliant on money sent home by migrants living and working in the United States, and poverty has contributed to the surge of violent street gangs in the past two decades. Quijano campaigned on a promise of tough policies to crack down on the gangs, and won over some voters. "It is just terrible. You can't even leave your house because there is danger everywhere. It is time to put an end to this," said Sandra Marin, 40, a shoe saleswoman. Sanchez Ceren rejects the idea of deploying the army to fight the gangs and instead vows to forge a political pact to break through gridlock that has kept a divided Congress from carrying out reforms to tackle crime and weak economic growth. He was a rural teacher before the civil war but joined the FMLN ranks and became a senior commander as it fought a series of U.S.-backed conservative governments. The FMLN won the last election when it put up a popular journalist, Mauricio Funes, as its candidate. He had no role in the civil war and has helped lead the FMLN toward more moderate leftist policies. Although many Salvadorans are terrified of the street gangs, a two-year-old truce between the Mara Salvatrucha (MS-13) gang and its rival, Barrio 18, has helped cut the number of murders in half from one of the highest homicide rates in the world to a 10-year low in 2013. Quijano, a 67-year-old former dentist who became San Salvador's mayor, accused the FMLN of making deals with gangs to win votes in areas controlled by the criminal groups. "Do you want to stay with a government that makes deals with criminals?" Quijano asked after he voted in a Roman Catholic school's basketball gym while supporters waved blue, white and red Salvadoran flags. Orlando Sanchez, a 73-year-old bricklayer, believes Arena, which was founded by members who backed death squads during the civil war, would steal public money if it regains power. "This country is poor because they left it that way," he said as he walked in a park in the center of the capital. El Salvador is known for its high-quality arabica coffee beans but it has been the country hardest hit by the spread of the tree-killing fungus roya in Central America. The fungus has infected more than 70 percent of the country's coffee plantations.