US Secretary of Defense Pete Hegseth told sailors and Marines on a warship off Puerto Rico on Monday that they were not deployed to the Caribbean for training but instead sent to the "front lines" of a critical counter-narcotics mission.

Hegseth's remarks came during a surprise visit along with the top US general to Puerto Rico amid escalating tensions with Venezuela, which US President Donald Trump's administration accuses of trafficking narcotics to the United States – allegations denied by Caracas.

"What you're doing right now – it's not training," Hegseth said aboard the USS Iwo Jima amphibious assault ship, in remarks shown in a video posted by the Pentagon on X.

"This is the real-world exercise on behalf of the vital national interests of the United States of America to end the poisoning of the American people."

Trump has ordered the Department of Defense to rename itself the Department of War, a change that will require action by Congress. The new name would apply to Hegseth as well, altering his title to "Secretary of War."

The USS Iwo Jima was positioned off the coast of Puerto Rico, a US territory located north of Venezuela in the Caribbean where Hegseth and the chairman of the Joint Chiefs of Staff, Dan Caine, visited earlier in the day.

Trump has long accused Venezuelan President Nicolas Maduro of narco trafficking, allegations Caracas has always denied. The Trump administration has ordered the deployment of 10 F-35 fighter jets to a Puerto Rico airfield to conduct operations against drug cartels, sources told Reuters on Friday.

Last week a US military strike in the Caribbean killed 11 people and sank a boat from Venezuela that Trump said was transporting illegal narcotics.

Members of the US Congress have asked for the legal rationale for the deadly strike, noting that the administration has yet to say how it knew who was in the boat or what it was carrying.

Administration officials had agreed to provide a classified briefing for congressional staff on Friday, but the meeting was abruptly rescheduled for Tuesday.

"There is no way on God's green earth you can say that whatever was in this boat presented any sort of imminent threat to the United States in a military sense of the word," Representative Adam Smith, of Washington, the top Democrat on the House of Representatives Armed Services Committee, said.

Venezuelan officials also criticised the Trump administration's actions.

"How can there be a drug cartel if there's no drugs here?" Venezuelan Vice President Delcy Rodriguez said on Monday, referencing figures she said show Venezuela does not produce cocaine and that the drug is largely smuggled via routes on the Pacific.

"They need to fix their GPS."

The Pacific Ocean is a bigger route than the Caribbean for maritime trafficking of cocaine, the United Nations Office on Drugs and Crime said in its 2023 Global Report on Cocaine.

Maduro's government has said a video posted by Trump of the strike is artificial intelligence and Maduro has alleged the US military is hoping to drive him from power. (Reuters)