* Some in opposition see 2014 FARC political participation
* Government wants speedy peace process with rebels
By Helen Murphy and Luis Jaime Acosta
BOGOTA, Jan 31 (Reuters) - As Colombia holds peace talks with FARC rebels, some opposition lawmakers have speculated the insurgents could take part in national elections next year, but the government is laying down terms that make that unlikely.
Interior Minister Fernando Carrillo said in an interview he is "moderately optimistic" that talks in Cuba to end five decades of war with the Revolutionary Armed Forces of Colombia or FARC will be successful, while saying he harbors a "big dose of skepticism."
Carrillo spelled out the government's position on how the rebels can enter Colombia's political process in an interview with Reuters at his office late on Wednesday.
"If they want to participate in politics, the first they have to do is lay down their arms," Carrillo said.
"That's why there is a negotiation, so that down the line they may have ways to participate in politics, but they must stop using weapons, compensate their victims and do it under conditions of international justice."
Colombia holds presidential and congressional elections in May 2014.
President Juan Manuel Santos took a gamble with FARC peace negotiations, which have failed in all attempts since the rebels took up arms in 1964. Santos wants the talks to be wrapped up this year, but the FARC have rejected time limits.
While some opposition lawmakers have raised the possibility that the FARC could participate in elections next year, the government has declined to speculate when rebel fighters could play an official role in Colombian politics.
"If there's an agreement then participation (in 2014) is possible," Ivan Cepeda, a lawmaker for the leftist Polo Democratico party, whose father was killed by right-wing paramilitaries in 1994, told Reuters.
"The government has said that once a general agreement is reached then certain measures can be implemented - because if we wait until the entire accord is completed there won't even be participation in 2024," said Cepeda.
A government source told Reuters, however, that the FARC entering the political system would be "impossible" during elections in 2014 and difficult for municipal elections a year later.
The insurgents, battling for a Marxist state for five decades, have increased attacks since ending a ceasefire last week. FARC seized then released three oil contractors and killed four soldiers, military sources said on Thursday.
The kidnappings and other violent incidents came days after the FARC made clear during negotiations it would continue to capture armed forces, possibly muddying the talks.
Even though most Colombians clamor for peace, integration into society would be the toughest part of any peace agreement with the FARC as people fret about rebels living and working in their neighborhoods and possibly representing them in Congress.
"The most difficult part isn't the signing of peace, but the post conflict," Carrillo, 49, said.
What may complicate FARC participation is the government's demand that the rebels compensate victims as part of the peace accord. Many of its leaders also are sentenced in absentia for crimes against humanity.
Political participation in 2014 "depends on the agreements reached, what's important is that there is no impunity in the process," said Carrillo, a lawyer and economist who previously held the post of justice minister.
Colombia has a long experience in demobilizing armed groups, but the process has not always been smooth.
Victims of right-wing paramilitary groups, which sprang up to protect wealthy rural landlords from leftist rebels, are still wrapped in complicated legal process to receive reparations, years after the militias demobilized.
Paramilitary fighters were not permitted as part of their integration to hold public office and some of the former mid-level commanders have since turned to drug running.
Carrillo highlighted an accord in 1990 with the M-19 rebel group, which was responsible for an assault in 1985 on the Palace of Justice that killed scores of people.
After reaching agreement with the government they won 19 seats that same year in a national assembly to change the constitution. Former M-19 rebel Gustavo Petro is currently mayor of Bogota, the second most powerful position in Colombia.
In talks with the FARC, the government has ruled out discussing major changes to Colombia's economic or political model, saying that if the guerrillas want to modify the system, they should run for election.
"Radical or utopian proposals won't prosper," said Carrillo. "The guerrillas can put them forward of course - because they are at a negotiating table - but there needs to be consensus." (Reporting by Helen Murphy; Editing by Cynthia Osterman)