A rebel of the Revolutionary Armed Forces of Colombia, or FARC, sits on the floor after being captured by the army in Neiva, Colombia, on Oct. 10, 2012. Peace negotiations between Colombia s government and Marxist rebels begin this week. (William Fernando Martinez/AP)

When peace negotiations between Colombia’s government and Marxist rebels begin this week, a country once accused of helping the guerrillas in their war against the government will be on hand: Venezuela, whose president, Hugo Chavez, has had an affinity with the insurgents.

For many Colombians, the populist firebrand is a destabilizing force who wanted to see the Revolutionary Armed Forces of Colombia, or FARC, take power late in the last decade from right-wing President Alvaro Uribe. Chavez once told the Venezuelan congress that Colombia’s guerrillas were fighting for a legitimate cause, and his government was accused of trying to isolate Uribe, a key U.S. ally in the war on drugs during an eight-year term that ended in 2010.

But Uribe’s center-right successor, Juan Manuel Santos, repaired tattered relations with Venezuela and then opted to take advantage of the admiration the FARC has for Chavez. Santos named Venezuela as one of four countries to participate in negotiations that begin Monday with the rebel group in Norway before moving to Cuba, where the bulk of the talks will take place.

And it has become clear in recent weeks that Chavez and his aides — particularly Nicolas Maduro, who was foreign minister until being named vice president this past week — have helped ensure that FARC commanders feel secure about meeting with Santos’s negotiators.

“Chavez has been extremely active on the peace process, not only logistically,” said Aldo Civico, a Rutgers University conflict resolution expert who has spoken to Colombian negotiators about the talks. “My understanding is that he has been able to talk to the members of the FARC negotiation team and encourage them to stay within the dynamic of the peace talks, to engage constructively.”

Norway, a country with a long history of brokering deals in conflicted countries, and Cuba, the host of the talks in the months ahead, will serve in the role of guarantors, with representatives from those countries sitting in on negotiations.

Venezuela and Chile, whose government is considered a close ally of Colombia’s government, are known as “acompañantes” — literally, company. They are to help with logistics, provide diplomatic support and “do whatever the parties ask them to do,” said a Colombian official familiar with the talks, speaking on the condition of anonymity because of the sensitivity of the negotiations.

Those who closely track the policies in the region said that Venezuela’s role is especially important because of the relationship Chavez and his closest associates have forged with FARC commanders during the Venezuelan leader’s 14 years in power.

“Without Venezuela, it would be very difficult to have a successful negotiation,” said Michael Shifter, president of the Inter-American Dialogue policy group in Washington. “They give some guarantees of legitimacy and credibility to the process and ensure that the talks stay on track.”

Santos, as defense minister for Uribe, oversaw some of the army’s biggest blows against the FARC, including strikes that killed some top commanders.

At the same time, Colombian military and police intelligence reported that the long, porous border Colombia shares with Venezuela had become a sanctuary for FARC units — a claim that was supported by people who live in border towns, rebel deserters and documents seized by Colombia’s army in abandoned rebel camps.

The United States also asserted that Venezuela had close ties to the FARC, and in 2008 it accused three top aides to Chavez of helping the rebels traffic in cocaine and battle Uribe’s government.

But upon his inauguration as president in August 2010, Santos moved fast to reopen a dialogue with Venezuela. “His main objective was to pursue a peace process, and he knew it would be hard to achieve without Chavez’s cooperation,” Shifter said.

The Venezuelan government, which had strenuously denied the accusations against it, responded positively to Santos’s diplomatic initiatives, noted Adam Isacson, a senior analyst on Colombia for the policy group Washington Office on Latin America.

“You have a president who wants to be seen as a peacemaker and wants to unite the region and cares about that,” Isacson said of Chavez. “Whatever advantage he saw in having a relationship with the FARC is probably now gone.”

Guerrilla negotiators have recently spoken publicly of Venezuela’s role in facilitating the talks and helping with the logistics that permitted them to get to Cuba for the preliminary negotiations that took place earlier this year with Colombian government representatives.

Chavez, too, has spoken about his government’s role in the talks, saying that his hope is for the guerrillas to reintegrate into society and continue their struggle through politics. He has also named a representative who will be in Cuba, Roy Chaderton, an experienced diplomat who has served in Washington as ambassador to the Organization of American States.

“With the guarantees Colombia’s government offers, with a good debate, with good talks, with a good accord, I think that the FARC could move into a political process,” Chavez said at a news conference last month in Caracas, Venezuela’s capital.

“They asked us for help,” he said of the FARC, “and I told the president, ‘Whatever needs to be done for Colombia’s peace, I’m willing to do it.’”