Colombia's president compared Nicolas Maduro to Serbian war criminal Slobodan Milosevic as he goes on a diplomatic offensive to corral the Venezuelan socialist, warning that he would be making a "stupid" mistake if he were to attack his U.S.-backed neighbour.

Ivan Duque made the comments in an interview Saturday with The Associated Press before travelling to New York where he is expected to condemn Maduro before the United Nations General Assembly as an abusive autocrat. Duque believes Maduro is not only responsible for the country's humanitarian catastrophe but is also now a threat to regional stability for his alleged harbouring of Colombian rebels.

"The brutality of Nicolas Maduro is comparable to Slobodan Milosevic," said Duque, who has called on the International Criminal Court to investigate Maduro for human rights abuses. "It must come to an end."

While Duque refused to rule out a military strike against the Marxist rebels he claims are hiding out across the border, he said any aggression by Venezuela's armed forces would immediately trigger a regional response that could include additional sanctions and diplomatic actions.

"If they consider doing something so stupid, they know what the consequences will be," said Duque.

Duque has ratcheted up pressure against Maduro in recent weeks after a small band of dissident leftist rebels decided to break with Colombia's historic peace process and take up arms against the state again, contending that the government has betrayed the accord aimed at ending over five decades of bloodshed.

Maduro, shown in early September, denies he is giving Colombian rebels refuge. (Marcelo Garcia/AFP/Getty Images)

At the UN, the young Colombian leader is expected to accuse Maduro of breaking a Security Council resolution passed after the Sept. 11, 2001, terrorist attacks by offering the rebels refuge.

The embattled Venezuelan president has repeatedly denied those accusations, and although he won't attend this year's General Assembly, his envoys are likely to levy similar charges against Duque, accusing him of failing to act against illegal armed groups plotting attacks against his government from Colombia.

"The Colombian oligarchy wants to lay the ground for an armed aggression against Venezuela," Communications Minister Jorge Rodriguez said recently.

Dangerous geopolitical implications

The growing tensions along the border have potentially dangerous and wide-reaching geopolitical implications involving the interests of Russia, China and the U.S.

At the U.S.'s urging, hemispheric allies recently dusted off a mutual defence treaty from the Cold War that requires the 19 signatory nations to come to the rescue of one another in the event of an external threat.

Shoes of Venezuelan migrants are displayed at Plaza Bolivar square in the Colombian capital, Bogota, earlier this month as part of a campaign against xenophobia. (Raul Arboleda/AFP/Getty Images)

Foreign ministers from most of the 1947 Rio Treaty nations are scheduled to meet Monday to weigh multilateral sanctions. Though the accord permits a joint military response, Duque insisted that is not the preferred course of action and that under no circumstances would Colombian troops be provoked.

"It's important that Duque at the U.N. will have this forum to present evidence about Colombian armed groups' activity in Venezuela, and it's also a chance to gauge world leaders' comfort levels with further ratcheting up pressure on Venezuela," said Adam Isacson, a defence analyst at the Washington Office on Latin America.

"But with Russia, China, and others opposing, it will be impossible to achieve consensus necessary to treat Venezuela, under the UN Charter, as a threat to peace and security," Isacson said.

Colombia has open-door policy

The Venezuela crisis is also stretching budgets across South America as over four million people flee an economic crisis worse than the U.S. Great Depression. The massive flight comes as Colombia, which has absorbed the largest number of migrants, is also grappling with skyrocketing coca production and implementation of the fragile and contentious peace accord with the Revolutionary Armed Forces of Colombia.

Despite the fiscal pressure on education and health budgets, Duque defended his open door policy, arguing that it allows Colombia to more effectively combat illnesses like measles, which it had previously eliminated but re-emerged with the arrival of more than 1.4 million Venezuelan migrants in recent years.

Closing the border will not curtail the exodus but rather force migrants to move on dangerous dirt trails that crisscross the porous 2,200-kilometre border between the two countries.

"The right policy is the one we have been embracing," said Duque, contrasting Colombia's response to the barriers recently erected in Ecuador and Peru. "If they decide to close the borders people will pass anyway but they will pass illegally and the control, for example of illnesses, will be more complex."

Duque, 43, rose from near obscurity within a spate of a few years with the help of former Colombian President Alvaro Uribe, the peace deal's chief critic. He served as a senator before winning the presidency last year on a law and order platform promising to reform key aspects of the accord.