President Obama welcomed Colombia’s leader to the White House on Thursday to celebrate one of the most successful U.S. aid efforts of the past few decades and pledge an additional $450 million in American assistance.

For more than 15 years the aid to the Colombian government and security forces flowed under a program called “Plan Colombia” that spanned three administrations. Over the years it grew to include a counterterrorism program, democracy development and trade deals. Obama and Colombian President Juan Manuel Santos in their White House appearance declared an end to that program and the beginning of a new effort called “Peace Colombia.”

The new name reflects a major turn of events for the nation that only 15 years ago was on the verge of becoming a failed state, dominated by guerrillas, paramilitary units and drug traffickers. America’s support to Colombia, sustained by small numbers of American military advisers, offers a stark contrast to the much larger and less successful efforts to stabilize Iraq and Afghanistan over the same period.

Today Colombia’s economy is one of the strongest in Latin America and the country’s longtime warring factions have been meeting in Cuba for peace talks. After a half-century of war the government and the country’s leftist guerrillas appear to be on the verge of historic peace deal.

Santos repeatedly thanked Obama for his efforts to support the talks. He also praised Obama for his outreach to Cuba, one of the Obama’s most consequential and controversial foreign policy initiatives.

“Thank you for your audacity in establishing diplomatic relations with Cuba,” Santos said.

Obama and Santos used much of their joint appearance to celebrate the successes of the last 15 years and cooperation between their two governments.

“There’s no denying Colombia’s remarkable transformation,” Obama said. “In short, a country that was on the brink of collapse is now on the brink of peace. . . . In Colombia today there is hope.”

Santos described the economic and political progress that Colombia has made in recent years as it has surged to become one of the strongest economies in Latin America.

“All of these advances are due in great part to the fact that 15 years ago when we were in such dire straits the Colombians received a friendly hand,” he said.

He thanked the United States not only for its military aid but also for its help with governance and rural development.

Obama urged Colombians to seize upon the moment of peace to build a prosperous and modern economy. Despite its advances in security, Colombia is still the world’s No. 1 exporter of cocaine. The $450 million in U.S. aid will be used to help strengthen Colombian security forces, reintegrate former fighters into society and extend the rule of law to jungle areas that have been outside the government’s control. The United States will also work with the Colombians to remove all of the land mines in the country over the next five years.

The de-mining effort will open up land to farming and help ease poor Colombians off of their dependence on cultivating coca, the raw material of cocaine. Production of the drug has increased sharply in the recent years.

“We all know its easier to start conflicts than end them,” Obama said. “We will be your partner in waging peace.”