Hegseth was accompanied by the top US military officer, General Dan Caine, and the two of them were welcomed by Jenniffer Gonzalez-Colon, the territory's governor, who announced the visit in a post on X.

She also thanked President Donald Trump "and his Administration for recognizing the strategic value Puerto Rico has to the national security of the United States and the fight against drug cartels in our hemisphere, perpetuated by narco-dictator Nicolas Maduro."

The United States alleges that leftist Venezuelan leader Maduro heads a cocaine trafficking cartel and recently doubled its bounty to $50 million in exchange for his capture to face drug charges.

A Pentagon official confirmed Hegseth had traveled to Puerto Rico, but provided no details.

Hegseth also visited the USS Iwo Jima -- one of eight US Navy ships that are involved in counter-narcotics efforts in Latin America -- on Monday, according to a post on X from a Pentagon account.

The post included a video of Hegseth addressing military personnel on the ship, telling them they were working to "end the poisoning of the American people" with drugs.

- US-Venezuela tensions -

Hegseth's visits to Puerto Rico and the Navy ship came around a week after the United States carried out a strike on an alleged drug-smuggling boat coming from Venezuela, an action that Trump said left 11 purported members of the Tren de Aragua gang dead.

Tensions between Washington and Caracas have soared, as the Pentagon accused Venezuela of buzzing one of its ships in the Caribbean, while Maduro has denounced the buildup of US military assets in the region.

In addition to the eight US warships in the region -- seven in the Caribbean and one in the Pacific -- Washington is also dispatching 10 high-tech F-35 jets to Puerto Rico.

Trump vowed Friday to shoot down Venezuelan military jets if they pose a danger to US forces, while Maduro on Sunday announced the deployment of 25,000 troops to the country's borders to ensure "the defense of national sovereignty, the security of the country and the fight for peace."

Drug-smuggling vessels are usually seized and their crews arrested once they are identified, making the US strike on the alleged traffickers an extremely rare event.

Trump's administration designated Tren de Aragua as a terror organization earlier this year, and the use of deadly force against the group's alleged members without due process echoes US actions against purported militants during its years-long "War on Terror."

US officials, including Hegseth, have said that strikes targeting drug cartels will continue.