Venezuelan President Hugo Chavez's insistence that his country doesn't need US help in fighting drug trafficking is raising diplomatic tensions as American officials warn of a surge in cocaine flights out of the country. New surveillance estimates released by US counter-drug officials say there has been a more than 16-fold increase in the amount of cocaine departing Venezuela by air since 2002. They say that rise - combined with a doubling of smuggling by sea - pushed the estimated flow of Colombian cocaine through Venezuela to 282 tons last year, four times higher than in 2004. But Chavez dismisses the estimates as an attempt to discredit his government and has rebuffed US offers of help. His vice president, Ramon Carrizalez, said Monday that Venezuela was cooperating internationally - just not on the US Drug Enforcement Administration's terms. "The DEA asks for freedom to fly over our territory indiscriminately," Carrizalez said. "Well, they aren't going to have that freedom. We are a sovereign country." Chavez suspended cooperation with the DEA in 2005, accusing its agents of espionage. Two DEA agents are left here, but US officials say their work has been severely restricted. "The drug traffickers are taking advantage of the gap that exists between the two governments," US Ambassador Patrick Duddy told reporters Saturday, citing the estimated fourfold rise in trafficking. Clearly displeased, Chavez warned the following day that Duddy is risking possible expulsion and could soon be "packing his bags." He suggested that before criticizing Venezuela, the US ought to get a handle on its own drug use and marijuana farming. Venezuela has pointed to large drug seizures as progress, and Carrizalez said some 4,000 people are behind bars on trafficking charges. US drug czar John Walters, however, recently told The Associated Press there was a glaring lack of corruption investigations or arrests of major traffickers. "The flow of cocaine through Venezuela - both north particularly through the Dominican Republic and Haiti but also into Europe through Africa and other places - has increased dramatically," Walters said. US officials have released surveillance data on 129 suspected drug flights originating in Venezuela during the first six months of 2008, a period during which only one such flight was spotted leaving heavily policed Colombia's Caribbean coast. The number of suspected drug flights from Venezuela in 2008 is on pace to exceed last year's 220. Many flights were traced by radar to the Dominican Republic, where small planes often drop cocaine at sea. Others were tracked to Mexico, Haiti, Honduras, Guinea and Guatemala. Carrizalez noted that most US-bound cocaine moves north by sea, largely along Colombia's Pacific coast. He accused US officials of spreading disinformation, saying Venezuela is making more strides now that it is not working with the DEA.