Washington — In a significant expansion of the war on drugs, the United States has begun training an elite unit of counternarcotics police in Ghana and planning similar units in Nigeria and Kenya as part of an effort to combat the Latin American cartels that are increasingly using Africa to smuggle cocaine into Europe.

The growing American involvement in Africa follows an earlier escalation of antidrug efforts in Central America, according to documents, Congressional testimony and interviews with a range of officials at the State Department, the Drug Enforcement Administration and the Pentagon.

In both regions, American officials are responding to fears that crackdowns in more direct staging points for smuggling — like Mexico and Spain — have prompted traffickers to move into smaller and weakly governed states, further corrupting and destabilizing them.

The aggressive response by the United States is also a sign of how greater attention and resources have turned to efforts to fight drugs as the wars in Iraq and Afghanistan have wound down.

“We see Africa as the new frontier in terms of counterterrorism and counternarcotics issues,” said Jeffrey P. Breeden, the chief of the D.E.A.’s Europe, Asia and Africa section. “It’s a place that we need to get ahead of — we’re already behind the curve in some ways, and we need to catch up.”

The initiatives come amid a surge in successful interdictions in Honduras since May — but also as American officials have been forced to defend their new tactics after a commando-style team of D.E.A. agents participated in at least three lethal interdiction operations alongside a squad of Honduran police officers. In one of those operations, in May, the Honduran police killed four people near the village of Ahuas, and in two others in the past month American agents have shot and killed smuggling suspects.

To date, officials say, the D.E.A. commando team has not been deployed to work with the newly created elite police squads in Africa, where the effort to counter the drug traffickers is said to be about three years behind the one in Central America.

The officials said that if Western security forces did come to play a more direct operational role in Africa, for historical reasons they might be European and not American.

In May, William R. Brownfield, the assistant secretary of state for international narcotics and law enforcement, a leading architect of the strategy now on display in Honduras, traveled to Ghana and Liberia to put the finishing touches on a West Africa Cooperative Security Initiative, which will try to replicate across 15 nations the steps taken in battling trafficking groups operating in Central America and Mexico.

Mr. Brownfield said the vision for both regions was to improve the ability of nations to deal with drug trafficking, by building up their own institutions and getting them to cooperate with one another, sharing intelligence and running regional law enforcement training centers.

But because drug traffickers have already moved into Africa, he said, there is also a need for the immediate elite police units that have been trained and vetted.

“We have to be doing operational stuff right now because things are actually happening right now,” Mr. Brownfield said.

Some specialists have expressed skepticism about the approach. Bruce Bagley, a professor at the University of Miami who focuses on Latin America and counternarcotics, said that what had happened in West Africa over the past few years was the latest example of the “Whac-A-Mole” problem, in which making trafficking more difficult in one place simply shifts it to another.

“As they put on the pressure, they are going to detour routes, but they are not going to stop the flow, because the institutions are incredibly weak — I don’t care how much vetting they do,” Professor Bagley said. “And there is always blowback to this. You start killing people in foreign countries — whether criminals or not — and there is going to be fallout.”

American government officials acknowledge the challenges, but they are not as pessimistic about the chances of at least pushing the trafficking organizations out of particular countries. And even if the intervention leads to an increase in violence as organizations that had operated with impunity are challenged, the alternative, they said, is worse.

“There is no such thing as a country that is simply a transit country, for the very simple reason that the drug trafficking organization first pays its network in product, not in cash, and is constantly looking to build a greater market,” Mr. Brownfield said. “Regardless of the name of the country, eventually the transit country becomes a major consumer nation, and at that point they have a more serious problem.”

The United Nations says that cocaine smuggling and consumption in West Africa have soared in recent years, contributing to instability in places like Guinea-Bissau. Several years ago, a South American drug gang tried to bribe the son of the Liberian president to allow it to use the country for smuggling. Instead, he cooperated with the D.E.A., and the case resulted in convictions in the United States.

Even more ominous, according to American officials, was a case in which a militant group called Al Qaeda in the Islamic Maghreb offered three of its operatives to help ship tons of cocaine through North Africa into Europe — all to raise money to finance terrorist attacks. The case ended this past March with conviction and sentencing in federal court in New York.

American counternarcotics assistance for West Africa has totaled about $50 million for each of the past two years — up from just $7.5 million in 2009, according to the State Department. The D.E.A. also is opening its first country office in Senegal, officials said, and the Pentagon has worked with Cape Verde to establish a regional center to detect drug-smuggling ships.

While the agency has not sponsored units in West Africa before, it has long worked with similar teams — which are given training, equipment and pay while being subjected to rigorous drug and polygraph testing — in countries around the world whose security forces are plagued by corruption, including the Dominican Republic, El Salvador, Guatemala and Panama.

It is routine for D.E.A. agents who are assigned to mentor the specially trained and screened units to accompany them on raids, but it has been unusual for Americans to kill suspects. Several former agents said the recent cases in Honduras suggested that the D.E.A. had been at the vanguard of the operations there rather than merely serving as advisers in the background.

By contrast, the effort in West Africa is still at the beginning stages, officials say. But the problems there are the same — and growing. Officials described one instance in which a methamphetamine lab was discovered in Africa, with documents suggesting that it had been set up by a Mexican trafficking organization. William F. Wechsler, the Pentagon’s top counternarcotics officer, said that observing drug traffickers’ advances into West Africa, and the response from American and local authorities, was like watching a rerun of the drug war in this hemisphere in years past.

“West Africa is now facing a situation analogous to the Caribbean in the 1980s, where small, developing, vulnerable countries along major drug-trafficking routes toward rich consumers are vastly under-resourced to deal with the wave of dirty money coming their way,” he said.