Colombian President Juan Manuel Santos applauded the deal to end his country's half-century conflict during an address at the United Nations Wednesday in which he hailed "one fewer war on the planet."

"Today I have come to the United Nations to announce, with my full voice and heart, that the war in Colombia is over," Santos said in an address to the General Assembly of his government's conflict with Marxist rebels.

"There is one fewer war on the planet," he added, striking a bright note amid the world body's deep divisions over how to end the bloodshed in Syria.

Addressing the General Assembly on the International Day of Peace, Santos had earlier presented a copy of the agreement, wrapped in the Colombian flag, to the 15 members of the Security Council, who gave him a standing ovation.

Santos launched negotiations with the Revolutionary Armed Forces of Colombia (FARC) after taking office in 2010, with the two sides sealing a deal on August 24 in Havana to end the Americas' longest conflict, which has claimed 260,000 lives.

The agreement will be ceremonially signed on Monday and put to a referendum on October 2, with Colombian voters tipped to approve it.

If approved, the FARC's estimated 7,500 fighters are to disarm under UN supervision.

Santos promised symbolic monuments to the end of the war after rebels give up their arms and are integrated into society.

"The weapons will be melted and turned into three monuments to peace -- in New York and Cuba, which were the seats of dialogue, and another in Colombia," he said.

US President Barack Obama said the peace agreement had taken "a lot of courage" and "hard work," in remarks ahead of his bilateral meeting with Santos on Wednesday.

"I could not be more supportive of these efforts."

"There are going to be a lot of challenges involved in implementation," he added.

"But I think this is an achievement of historic proportions. It ultimately will be good for the region as well as the people of Colombia."

US Secretary of State John Kerry will travel to Colombia for Monday's signing of the peace deal in Cartagena.

Santos said he expected the agreement to turn the FARC into a peaceful, democratic political force and to lead to a better quality of life for people in the countryside who were most affected by the 52-year war.

The accord is historic for setting up a mechanism for justice involving an armed group not imposed by outside mediators, he said.

"Those responsible for international crimes and other serious crimes will be investigated, tried and punished," Santos said.

The end of the war would also halt the role of drugs in funding the rebellion, he added.

Besides curbing trafficking, he said, the deal will reduce deforestation driven by coca cultivation.