The chief of the UN mission verifying parts of Colombia’s peace accord implementation has had a rare public disagreement with the Colombian government.

On Tuesday, Jean Arnault urged officials to do more to keep former FARC fighters from slipping through the cracks. He pointed out some alarming things:

“A very high percentage of ex-FARC members are not in the ETCRs [Territorial Spaces for Training and Reincorporation, the former cantonment zones where FARC demobilized, but from where they are now free to leave]. The phenomenon calls for attention. The ex-guerrillas were about 8,000 on May 20 in the Village Zones [the cantonment zones] when the storage of FARC weapons concluded. As of August 15 [the day when ex-FARC members were allowed to leave], 70 percent remained. Today we estimate at 45 percent the number that still remain at the ETCRs.

“…[T]he greatest determining factor for these departures is effectively, according to the interviews the Mission has carried out, the loss of confidence in the perspectives that the ETCRs offer. Many expectations unmet for a long time. The El Gallo ETCR and the Policarpa ETCR have been almost totally abandoned, and their residents have moved to places that seem more favorable to them. Of other ETCRs, which weren’t abandoned, groups of 20 to 50 ex-guerrillas are leaving for the same purpose.”

Why would so many ex-guerrillas be disappearing without a trace? Arnault’s response defies belief:

“[A]s of today, a framework plan for reincorporation [of ex-combatants] still doesn’t exist. That was the central mandate of the National Reincorporation Council established a little less than a year ago.”

Faced with such a dire warning couched in diplomatic language, Colombian officials struck a wounded tone. Here’s the high commissioner for peace, Rodrigo Rivera:

“We’re surprised by Mr. Arnault’s declarations. Diplomatic channels exist to propose the sort of reservations that he proposes, and I see they weren’t sufficient. This sows the notion that there’s a sort of diaspora of FARC ex-combatants from the Territorial Spaces. …The purpose of the spaces was that they be temporary, they aren’t confined there and the UN knows it.”

Rivera is mistaken. The time for quietly routing things through diplomatic channels is over.

A core element of any peace process is the careful reintegration of ex-combatants. Thousands of unemployed, under-educated people with combat skills are being set loose in a country already challenged by organized crime, narcotrafficking, and ungoverned territory. That no plan is in place to occupy them, or even to keep track of them, is a failure at the most elemental level.

It’s worth noting that the day before Arnault and Rivera were exchanging words in Bogotá, Colombia’s foreign minister was in Washington. One of the things María Ángela Holguín brought up with Secretary of State Rex Tillerson was the government’s oft-expressed desire to enter the Organization for Economic Cooperation and Development (OECD), the Paris-based club of 35 wealthy nations.

Note the incongruity between Colombia’s first-world aspirations and the UN’s very basic warnings.

Granted, Colombia is in a budget crunch triggered by the drop in oil prices. And yes, the President’s governing coalition is fragile, and public opinion toward the peace accord is tepid as the March legislative and May presidential elections approach.

But it should not be too taxing for Colombia to fund a collective reintegration plan for the former FARC, right now, before thousands of seasoned fighters melt away and join the ranks of organized crime. The cost is not prohibitive. At least, not prohibitive for a country knocking on the OECD’s door.

We’re talking about 12,000 people. How much would that cost? Let’s ballpark it.

• Each one receives 10 million Colombian pesos—a “normalization” payment plus seed money for a productive project—plus a stipend of about 663,000 pesos per month for 24 months. That all adds up to about 26 million pesos, or US$8,730 per ex-guerrilla. For 12,000 guerrillas, the price tag here would be about US$105 million.
• Perhaps 70-75 percent of the 12,000 would like to work land, through cooperatives. That land would need to be purchased. Let’s say 4 hectares each (10 acres) times 9,000 people: 36,000 hectares, the size of a single cattle ranch in the country’s eastern plains. Even at a steep price like US$2,000 per hectare, that would add US$72 million to give land to ex-FARC cooperatives.
• Many of the demobilized would need basic education and vocational training. Say, US$3,000 per person for 6,000 people. US$18 million.
• All need psychosocial support, medical attention, and just basic monitoring. Assume US$5,000 per person times 12,000 — US$60 million.
• That brings us to a total reintegration price tag of US$255 million. I’m sure this estimate is missing a lot—and there are some items in the peace accord, like support to ECOMÚN, a FARC cooperative, that don’t have specific price tags. So let’s add another 50 percent, and another 10 percent for administrative costs, and call it US$408 million.

US$408 million over, say, two years. Colombia’s one-year GDP is about US$285 billion. Colombia is currently collecting about US$80 billion per year of that as taxes. The cost of reintegration would be about 0.26 percent of that annual budget. Money can’t be what’s stopping the ex-FARC from being reintegrated.

Why Colombia hasn’t been able to reach up and grab even this “low-hanging fruit” is a mystery bedeviling most of us. As Colombia’s OECD aspirations make clear, the problem isn’t money.

It seems more like an ossified bureaucratic culture rendering the government almost inoperable. Combined with that familiar bugbear, “a lack of political will.” This term gets thrown around a lot but is really a “black box” obscuring deeper, structural problems like social power relations, corruption and criminality, and economic inequality.

These are poor reasons to risk a slide back into violence and victimhood in what, for now at least, are post-conflict regions of the country. The UN’s warnings about reintegration are on the mark. If anything, they’re too muted.