Havana, Cuba (CNN) For Cuban officials on the front lines of the fight against drug trafficking, the Trump administration's threat to roll back improved relations between the United States and the communist-run island comes at a dangerous moment.

In rare interviews, two officials in charge of Cuban drug enforcement efforts told CNN they have seen an increase in smuggling just as US cooperation seems to be wavering.

The officials, both with Cuba's Interior Ministry, said that since President Barack Obama ended the "wet foot, dry foot" provision in 2016 that gave Cubans preferential immigration treatment, smugglers who once brought Cuban migrants into the United States aboard high-speed boats are now increasingly bringing drugs across the Straits of Florida.

"There's been a readjustment," said Lt. Col. Héctor González Hernández, head of Cuba's Counterdrug Directorate, "We have evidence that the criminal networks are changing from human trafficking to drug trafficking or both at the same time."

So far in 2017, Cuban officials say they have seized or recovered nearly 3 tons of marijuana and cocaine from drug traffickers, more than triple the amount of drugs they seized during the first six months of last year.

'We are waiting to see what happens'

At the same time, Cuban officials said, two meetings with their counterparts in the United States scheduled to take place in 2017 to discuss drug trafficking have either been canceled or postponed as the Trump administration prepares to roll back US-Cuban relations that thawed under the Obama administration.

"We are waiting to see if it happens," Col. Victor Lopez Bravo, of the Cuban coast guard and border patrol, said of the meetings in which law enforcement officials from both countries discuss tactics and share intelligence. "It's up to the United States to announce and invite us to the next meeting. We hope it happens because it really is beneficial for both countries," he said.

Trump is expected to announce in a speech before an anti-Castro crowd in Miami on Friday that he will roll back parts of the Obama administration's opening with Cuba, the most significant improvement to US-Cuban relations in decades.

Trump's Cuba policy is being finalized, US officials said, but he is expected to revert to a tougher line on Cuba and blast the Cuban government for human rights abuses. One measure still being considered, a White House source said, is barring Cuban officials and Communist Party members from visiting the United States.

If adopted, the measure could potentially chill the nascent collaboration on a wide range of issues, including drugs.

Castro decreed 'zero tolerance' on narcotics

Just 90 miles from Key West, Cuba's 3,570 miles of coastline and more than 4,000 keys have long made the island a favored area of operation for smugglers, bringing alcohol during Prohibition and later drugs to the United States.

Pre-revolution Havana was run by the American Mafia and awash in illegal drugs. For many American visitors the city's debauched nightlife was their first opportunity to snort cocaine or visit an opium den. "One could obtain anything at will," wrote Graham Greene of the city, "whether drugs, women or goats."

But in 1959, when Fidel Castro took power, he decreed a policy of "zero tolerance" on narcotics. Anyone in possession of drugs ensnared by the revolution's layers of police and informants faced a lengthy prison sentence, or sometimes a firing squad.

Nearly overnight, drugs in Cuba -- other than some marijuana grown deep in the mountains or the rare kilo of cocaine that washed up from a smuggling run gone bad -- became impossible to obtain.

But in 1989, the Cuban government's reputation for combating drug trafficking was dealt a devastating blow when 13 military and interior ministry officials were discovered to be conspiring with drug cartels to allow shipments of cocaine through Cuban territory to the United States.

Four Cuban officials, including a highly decorated general named Arnaldo Ochoa, were tried and executed for their roles in the scheme, and dozens more were purged as part of a scandal that rocked Cuba at the highest levels.

Since then, US officials say Cuba has stepped up efforts to crack down on smuggling and cooperated with the United States, a rarity in the Caribbean, where rampant corruption often means the officials tasked with fighting drug trafficking benefit handsomely from turning a blind eye.

Tons of illegal drugs intercepted

Cuban officials told CNN that, despite political differences with the United States, they have provided key intelligence to help capture smugglers. According to Bravo, the Cuban Interior Ministry official, the Cubans in the last 10 years have tipped off the United States to over 500 smuggling operations, and from 2003 to 2016 seized or recovered over 40 tons of marijuana, cocaine and hashish.

"We have prevented a huge quantity of drugs from coming into the US," he said.

In 1996, Cuban officials turned over to the United States 6 tons of cocaine seized from a Colombian freighter.

Since 2000, the US Coast Guard has based a liaison officer in Havana to work with Cuban officials on maritime issues, including drug interdiction.

In December 2014, President Obama announced he would pursue a new policy with Cuba that moved from Cold War-era confrontation to focus on areas of mutual interest.

After the policy shift, Cuban and US drug enforcement officials began holding regular meetings in Cuba and Florida and in 2016 signed an agreement on law enforcement cooperation that for the first time allowed US and Cuban boats chasing drug traffickers to be in direct contact during those pursuits.

Previously, US and Cuban anti-drug units were not allowed to share information without going through their superiors in Havana and Miami, a delay that Cuban officials said often gave smugglers ample time to slip away.

Pipeline switches from Mexico to Caribbean

Cuba's assistance, according to US officials, has been a rare bright spot as drug traffickers shift back from smuggling through Mexico to routes in the Caribbean.

"Despite its location between the largest exporters of illegal drugs in the hemisphere and the US market, Cuba is not a major consumer, producer or transit point of illicit narcotics," said a 2016 US State Department report on drug trafficking. "Cuba's intensive security presence and interdiction efforts have kept supply down and prevented traffickers from establishing a foothold."

Recently, Cuban officials said they have shared intelligence they obtained with US counterparts on marijuana grow houses operated by Cuban immigrants in Florida and on drug rings trying to smuggle synthetic drugs into Cuba from the United States to supply the island's fast-growing tourist market.

Now Cuban officials worry that scaled back relations could degrade the improved cooperation in the fight against drug traffickers.

"The biggest impact will be felt in the United States," said Bravo. "Cuba is not a country that the drugs are coming to. Fundamentally the drugs go north. If there is a step backward in the cooperation the impact will be felt in the US."