Colombians march in polarizing bid to make peace with FARC BOGOTA (Reuters) - Waving balloons and dressed in white, tens of thousands of Colombians marched in Bogota and across the nation on Tuesday in a polarizing gathering for peace that critics slam as a show of support for Marxist FARC rebels. Throngs of people chanting "We want peace" advanced toward the capital's main square, Plaza Bolivar, a few blocks from where former presidential candidate Jorge Eliecer Gaitan was assassinated on April 9, 65 years ago. "The nation is expressing its rejection of violence, violence that has caused so many wounds and so much pain," President Juan Manuel Santos said as he joined the mass. The march, backed by leftist politicians Ivan Cepeda and Piedad Cordoba, aims to show a united front against violence and in favor of peace. But it has divided the nation, with many believing the movement is a launch pad for the Revolutionary Armed Forces of Colombia, or FARC, to enter politics. Santos late on Monday called on the nation to reject what he called "enemies of peace" and join the march to show support for his historic bid to bring an end to five decades of bloodshed with the rebels. "Peace is the sublime objective of any society," Santos said. Colombia, at war with the FARC since 1964, in November launched a controversial bid to negotiate peace with the rebels during talks in Havana, Cuba. Critics say Santos is negotiating behind the nation's back and handing the FARC whatever they want. Former President Alvaro Uribe, once a Santos ally, charges that the FARC, mostly funded by extortion and drug trafficking, will trick the nation as it has in previous peace talks and get away with crimes without being punished. Uribe said the FARC has helped fund the march. "My opposition to the peace process isn't against peace, it's against impunity," Uribe said on his Twitter account. Government and rebel negotiators are seeking common ground on a five-point agenda, beginning with the thorniest issue of rural development and land reform. Social inequality in Colombia's vast rural territory is considered the root of the conflict - with land ownership concentrated in very few hands. "This movement shows the people of Colombia are completely decided in favor of peace," Cepeda told Reuters on Tuesday. "We are negotiating peace in Havana but today shows the process is backed by multitudes," the lawmaker said. The march is being held on the anniversary of the murder of Gaitan, a leftist politician gunned down as it became clear he would win the 1948 presidential election and fight for the rights of the poor. His death unleashed a wave of violence and paved the way for the founding of the FARC. "We were born into violence, my children were born into violence," said Gustavo Rodriguez, 54, a farmer from Tolima province as he walked toward Bogota's historic center. I believe this process will bring peace. It's not that we support Santos, it's not that we support the FARC, it's that we live in the middle of gunfire. But the rebels took advantage of the breathing space to train fighters, build more than 25 airstrips to fly drug shipments and set up prison camps to hold hostages. Additional reporting by Eduardo Garcia; Editing by Jackie Frank and Eric Walsh