The planes will join US warships already deployed to the southern Caribbean as Trump steps up pressure on Venezuelan President Nicolas Maduro, whom the United States accuses of leading a drug cartel.

The standoff has grown in recent days as the Pentagon said two Venezuelan military planes flew near a US Navy vessel in international waters Thursday in a "highly provocative" move.

US forces on Tuesday blew up an alleged drug boat in the Caribbean that Trump said belonged to the Tren de Aragua, a Venezuelan criminal organization he tied to Maduro, killing 11 people.

The high-tech F-35 jets are being deployed to an airfield in Puerto Rico, a US Caribbean island territory of more than three million people, the US sources said on condition of anonymity.

Maduro -- a leftist firebrand whose last election in 2024 was seen by Washington as illegitimate -- has denounced the US build-up as "the greatest threat our continent has seen in the last 100 years."

Declaring his country prepared for "armed struggle in defense of the national territory," he has mobilized Venezuela's military, which numbers around 340,000, and reservists, which he claims exceed eight million.

"If Venezuela were attacked, it would immediately enter a period of armed struggle," Maduro told foreign correspondents.

- 'Highly provocative' -

Tuesday's deadly US attack on what Washington said was a drug-carrying boat was a major escalation, as well as an unusual use of the US military for what has historically been a law enforcement issue.

"Venezuela has been very bad, both in terms of drugs and sending some of the worst criminals anywhere in the world into our country," Trump told reporters in the Oval Office on Wednesday.

Trump has so far deployed five US vessels -- a guided missile cruiser, three guided missile destroyers and a nuclear-powered fast attack submarine -- to the Caribbean as part of the counter-drug mission.

There are also 4,000 US Marines reportedly involved in the deployment.

The US Department of Defense -- which Trump is set to rebrand as the "Department of War" on Friday -- said that two "Maduro regime" aircraft flew near a US vessel on Thursday.

"This highly provocative move was designed to interfere with our counter narco-terror operations," it said on X.

It did not give further details. Venezuela has 15 F-16 fighter jets purchased from the United States in the 1980s plus a number of Russian fighters and helicopters.

US Secretary of State Marco Rubio defended the new aggressive approach towards what Washington calls "narcoterrorist" groups on a trip to Latin America this week.

"What will stop them is when you blow them up, when you get rid of them," Rubio said in Mexico on Wednesday.

"If you're on a boat full of cocaine or fentanyl headed to the United States, you're an immediate threat to the United States."

Caracas accused Washington of committing extrajudicial killings in the attack.