US President Donald Trump has made cracking down on drug cartels a central goal of his administration, part of a wider effort to limit migration and secure the US southern border.
While US Coast Guard and Navy ships regularly operate in the Southern Caribbean, this buildup is significantly larger than usual deployments in the region.
A US official, speaking on the condition of anonymity, on Thursday said seven US warships, along with one nuclear-powered fast attack submarine, were either in the region or were expected to be there in the coming week.
Venezuelan President Nicolas Maduro has denounced the moves. The Pentagon has not indicated publicly what exactly the US mission will be, but the Trump administration has said it can now use the military to go after drug cartels and criminal groups and has directed the Pentagon to prepare options.
Venezuela on Thursday complained to United Nations Secretary-General Antonio Guterres about the US naval buildup, accusing Washington of violating the founding UN Charter.
"It's a massive propaganda operation to justify what the experts call kinetic action - meaning military intervention in a country which is a sovereign and independent country and is no threat to anyone," Venezuela's UN Ambassador Samuel Moncada told reporters after meeting with Guterres.
On Thursday, the White House said Trump was ready to use "every element of American power to stop drugs from flooding into our country".
"Many Caribbean nations and many nations in the region have applauded the administration's counter drug operations and efforts," White House press secretary Karoline Leavitt told reporters.
The Trump administration designated Mexico's Sinaloa Cartel and other drug gangs, as well as the Venezuelan criminal group Tren de Aragua, as global terrorist organisations in February. Part of the buildup is the USS San Antonio, USS Iwo Jima, and USS Fort Lauderdale. The ships are carrying 4500 service members, including 2200 Marines, sources have told Reuters.
The US military has also been flying P-8 spy planes in the region to gather intelligence, officials have said, though they have operated in international waters.
"Our diplomacy isn't the diplomacy of cannons, of threats, because the world cannot be the world of 100 years ago," said Maduro, whose government said last week it would send 15,000 troops to states along its western border with Colombia to combat drug trafficking groups.
Maduro has also called for civil defence groups to train each Friday and Saturday.
Maduro's government regularly accuses the opposition and foreigners of conspiring with US entities such as the CIA to harm Venezuela, accusations the opposition and the US have always denied. It characterises sanctions as "economic war".
