MIAMI — The Trump administration has added Colombia to a list of nations failing to cooperate in the drug war for the first time in nearly three decades but issued a waiver blocking any major aid cut to what has traditionally been the staunchest U.S. ally in Latin America.

The move Monday reflects a decade-long boom in cocaine production in Colombia and a slowdown in coca eradication under President Gustavo Petro’s leftist administration.

The U.S. last added Colombia to the list in 1997 when the country’s cartels had infiltrated the highest levels of power. Since 2000, successive U.S. administrations have sent billions of dollars in aid to Colombia, but the cooperation began to unravel a decade ago when a program to spray coca fields with glyphosate was suspended.

Under U.S. law, the president annually must identify countries that have failed to meet obligations under international counternarcotics agreements during the previous 12 months.