Bogota (AFP) - Nicolas Maduro's days as president of crisis-ravaged Venezuela are numbered, his outgoing Colombian counterpart Juan Manuel Santos told AFP.

"I can see it happening in the near future," said Santos, pointing to the International Monetary Fund's latest projection that Venezuela's inflation will hit one million percent this year.

"A country with the level of inflation that Venezuela has... that regime has to fall."

Relations between the two heads of state have been tense for years with Maduro describing Colombia as a US "lackey" and Santos predicting imminent "regime change" in Venezuela ahead of presidential elections in May, won by Maduro but that were boycotted by the opposition.

Hundreds of thousands of Venezuelans have flooded into Colombia as they flee food and medicine shortages, as well as failing public services in their crisis-torn country.

Venezuela has been gripped by a four-year long recession which Maduro blames on opposition "sabotage."

He also disputed a claim by a group of leading Venezuelan universities that put extreme poverty in the country at 61 percent. Maduro says it's only 4.4 percent.

"He is in a state of denial," Santos said of Maduro. "He is irrational because he says no, there is no crisis there and he does not need help."

- Duque threat to peace deal -

Last year Colombia repeatedly accused Venezuelan troops of territorial incursions while Santos has also been angered that Marxist National Liberation Army (ELN) guerrillas have found shelter in socialist Venezuela.

"Without a doubt, some ELN commanders are in Venezuela, we've known that for a long time," said Santos.

"We've killed many of their leaders and regional chiefs there."

Tensions between the two countries are hardly likely to ease once Santos leaves office next week, with hard-right president-elect Ivan Duque set to take over.

As well as stoking unease across the border, Duque's ascendancy could have repercussions for the peace accord Santos signed with FARC rebels.

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That deal may have won Santos the Nobel Peace Prize but proved a poisoned chalice politically as his domestic popularity plummeted.

Santos believes it was worth it, though, not for himself, but for the country.

"My legacy will defend itself, you can see the results," he said. "There is peace, the FARC is a political party, it's there.

"It's the Colombian people that will defend peace because it's not my peace, nor that of my government, but of all Colombians.

"It's the greatest gift that any society can have, Colombians have to and will defend peace."

Following a half-century of armed conflict, FARC guerrillas signed a disarmament deal with the government in December 2016 and were transformed into a political party with 10 seats reserved in the senate.

- 'Making progress' -

Although the FARC laid down its arms, barring a few dissidents, the ELN has continued its own struggle, although Cuban-hosted peace negotiations are ongoing.

"What we're delivering, and what all the international organizations say, is that it's a very complete peace, very deep. This agreement with FARC has no precedent in any other country," said Santos.

"Now, we're continuing to negotiate with the ELN, we're making a lot of progress, we'll see if we can sign a ceasefire before August 7, even if it's temporary and a framework agreement."

August 7 is the day Santos hands over the presidency to Duque, who upon his election in June vowed to make "corrections" to the peace deal, which he criticized for being too lenient on former rebels.

Santos, though, sees no reason to fear that Duque will undo his hard-won achievements.

"The country is already too polarized. President-elect Duque told me himself in this very (presidential) palace: 'Look, I'm going to continue with the policies I think are working, correct those that aren't working and I'll introduce some of my own projects and initiatives. I won't govern with a rearview mirror.'

"All this seems logical and convincing to me. I hope he achieves it because that's what every government should do."

But while Santos enjoyed success in bringing left-wing guerrillas to the table, he has been unable to tackle Colombia's violent drug trade, which has left thousands dead.

The fight against drugs cannot be "won by just one country" and needs to be tackled on a "multilateral" level, he said.