Colombian President Juan Manuel Santos says he hopes Europe can provide funds to help him strike a "last chance" deal with leftist guerrillas after half a century of conflict.

During a lightning tour of six countries in five days next week, Santos will lobby for the creation of a European fund for the post-conflict period, should his government clinch a historic deal with the Revolutionary Armed Forces of Colombia (FARC).

"It's the oldest conflict in the Western world," Santos told AFP in an interview at the presidential palace in Bogota -- his first with an international news agency since his re-election in June.

"If we manage to secure peace, it will have an impact far beyond Colombia's borders."

The center-right leader is expected to discuss gains made in nearly two years of peace talks with the FARC when he meets with his counterparts in Belgium, Britain, France, Germany, Portugal and Spain.

The talks, which have been held in Cuba without a ceasefire on the ground in Colombia, have led to an agreement in principle on the need to fight drug trafficking -- an argument that should resonate in Europe.

"Colombia has been the world's cocaine supplier for the past 35-40 years," stressed Santos.

He intends to ask his European partners to boost their investments in alternative crops to coca, the plant from which the drug is made and one that has served as the main source of income for many farmers in the Andes mountains.

- 'Image problem' -

"We have an image problem, that's for sure. But the facts speak loudest about our evolution," Santos said.

The leader of Latin America's fourth-largest economy, with 47 million inhabitants and forecast to record five percent growth this year, also plans to ask foreign investors to fund economic projects to help demobilized fighters reintegrate in society and find jobs.

At stake is one of the biggest challenges Santos faces: making sure former rebels do not join drug trafficking gangs, as many former far-right paramilitary fighters have done.

The right-wing fighters have also played a role in Colombia's long-running conflict, which has left 220,000 people dead and displaced more than five million people in 50 years, according to official figures.

"If some of them think they will carry on as bandits, they will find the full force of the law will fall upon them," Santos warned.

- Cart before the horse? -

The Colombian president -- perhaps surprisingly -- said he hoped peace would have a "very positive" impact on climate change and biodiversity, as the fight against armed groups that have taken refuge in jungle areas has damaged the environment, water sources and tropical forests.

But by pleading with the international community before it even has a peace deal, is Colombia putting the cart before the horse?

The government has yet to formalize contacts with the National Liberation Army (ELN), the other leftist rebel group that counts 2,500 fighters, as compared with 8,000 active FARC members.

Reluctant to impose a hard deadline for a deal, Santos nonetheless hopes to clinch a final agreement with the main guerrilla group next year ahead of October 2015 regional elections, when a referendum could be put to a vote.

"I have no doubt at all that Colombians will support peace," he told AFP.

But Santos also warned: "Many believe this is the last chance, because it is difficult to bring together the conditions for success."