* Colombia, rebels began peace talks this week
* FARC calls land restitution program a "trap"
* Santos says the reform makes the rebels nervous
By Jack Kimball
BOGOTA, Oct 19 (Reuters) - Colombian President Juan Manuel Santos on Friday defended his signature law that returns land seized by illegal armed groups to peasants after leftist rebels assailed the measure at the start of peace talks.
Negotiations to end five decades of war started out bumpy this week when Ivan Marquez, lead negotiator for the Revolutionary Armed Forces of Colombia, or FARC, called Santos' restitution law a "trap."
"When these gentlemen from the FARC say this law is a lie it's because ... they know full well that this is something that takes away from one of their propaganda banners," Santos said on his radio program.
One of the FARC's main grievances since taking up arms in 1964 has been the unequal distribution of land, which has been concentrated in the hands of a few since the Spanish conquered the region around the 16th century.
Since coming to power in 2010, Santos' government has pushed through reforms such as the restitution of land to displaced peasants. The move was seen as paving the way for peace talks with the rebels.
Over the conflict's long history, millions of Colombia's rural poor have been forced from their homes by FARC rebels and right-wing paramilitary groups who later used the land to fund their fighting forces.
BOON FOR CORPORATIONS?
On Thursday Colombian government and rebel negotiators agreed to meet in Cuba in mid-November to start what are likely to be difficult talks with the top issues being rural development and land.
Marquez railed against the restitution law at a press conference in Norway.
"Land titles as the current government has designed it are a trap," the guerrilla leader said.
He argued that returning land to peasants who lack the means to make it productive would likely encourage them to sell it cheaply to international corporations.
Various peace efforts in Colombia since the 1980s have brought mixed success, with some smaller armed groups demobilizing. But the FARC, Latin America's biggest rebel group, has pressed on, funded in large part by drug trafficking.
The guerrillas were widely seen to have used previous negotiations to rearm and rebuild their ranks. Right-wing elements linked to Colombia's political establishment also were accused of undermining talks.
The FARC, which traces its roots to the peasant self-defense forces of the 1950s that fought against wealthy landowners, wants to change Colombia's economic system, which Santos' government flatly rules out.
Colombian newspapers and analysts, pointing out the discord between the two sides when talks opened this week in Norway, said the road forward would be very long.
Others were less pessimistic.
"It's important not to over-interpret what the FARC said. They needed to use this as a platform for voicing their political agenda rather than showing flexibility for the talks," said Christian Voelkel, Colombia analyst for the International Crisis Group think tank.