Colombia's last active rebel force, the leftist National Liberation Army (ELN), promises to release a hostage Thursday to clear the way for peace talks with the government.

President Juan Manuel Santos wants the talks to seal a "complete" peace after 52 years of conflict, following an accord with the biggest rebel force, the Revolutionary Armed Forces of Colombia (FARC).

But deep differences remain with the ELN, as one of its western commanders, Danilo Hernandez, told AFP in an interview in the jungle this week.

Here are five of the tough issues that will face the sides if they launch formal peace talks as planned on February 7:

- Land -

The communist ELN insists its demand of land rights for the rural poor remains as valid now as when it took up arms in 1964.

"The government has said there will be no concessions on private property, which is what most impoverishes the poor," said Hernandez, commander of the Resistencia Cimarron guerrilla front.

"The revolutionary armed struggle is still fully valid. As long as the necessities that were at the root of this insurgency exist, we will have to keep fighting."

- Violence -

Hernandez also complained that the government will not compromise on its "military doctrine," protecting state forces from prosecution over the violence.

"A large percentage of the homicides in Colombia are committed by the armed forces and the police along with paramilitary groups which are an arm of the state."

The right-wing paramilitaries were officially disbanded in 2006, but "they are still active and are growing in strength," Hernandez said.

He said pressure from state forces against the ELN had intensified since the government made peace with the FARC.

- Hostages -

The ELN has promised to release it most prominent hostage, former lawmaker Odin Sanchez, as a condition for talks.

But it has not yet promised a formal end to its hostage-taking.

"The government established the conditions for the dialogue in the middle of a conflict," Hernandez said.

"The question of whether being at war implies (that such) detentions (are necessary) will be discussed in the negotiations."

- Money -

Under their peace accord, the FARC and the government agreed to substitute legal crops for the coca leaves that have fueled the conflict and the drugs trade.

As well as by taking hostages, Hernandez said the ELN finances itself by levying a "tax" on buyers of coca, the raw material used for making cocaine.

He did not comment on how an end to coca crops might affect the ELN's finances.

"The ELN has no direct link to the growing" of the coca, he said, however. "We have no other link to drug trafficking."

- Good will -

Decades of violence have yielded a mood of bitter ELN distrust of the government.

However, the ELN has "always" had a desire for peace, said Hernandez.

He declined to say whether he thought the peace process could be completed by the time Santos leaves office next year.

"We are in no hurry to finish," he said.

The FARC spent four years negotiating with the government before reaching an accord.

"The government has laid down red lines on issues that are at the origin of the conflict," Hernandez warned.

"If no solution is sought for those, it gets harder and harder to achieve."